CURRENT ELECTRICITY
1.
What are the minimum requirements to cause the flow of current?
A. A voltage source, an ammeter, a conductor and an insulator
B. A voltage source, a switch and a resistor
C. A voltage source and a conductor
D. A voltage source, a conductor and an insulator
2.
Out of the following, select the best conductor of electricity.
A. Graphite
B. China clay
C. Porcelain
D. None of these
3.
Which of the following statements is correct?
A. The resistance does not play an important role in electrical engineering.
B. The resistance of a wire does not depend upon its material.
C. The resistance of most of the materials is independent of the temperature.
D. The resistance of conductor is the hindrance by which the conductor opposes the flow of the
current.
4.
Resistance of a conductor increases when
A. its length increases
B. its area increases
C. both length and area increases
D. specific resistance is kept constant
5.
The specific resistance ρ depends upon
A. The area of cross-section and the length of the conductor
B. The material of the conductor, its area of cross-section and length
C. The nature of the material of the conductor only
D. The area of cross-section of the conductor
6.
The specific resistance ρ is defined as
A. resistance of a conductor which has a length of 1 m and cross-section of 1 m2 at 20oC
B. resistance of any conductor at 25oC
C. resistance of any conductor at 20oC
D. resistance of a conductor which has a length of 1 m and cross-section of 1 cm2 at 20oC
7.
The resistance of a conductor, when its temperature is increased
A. remains constant
B. increases
C. varies
D. decreases
8.
It was experimentally found by James Prescott Joule that the heat produced in a current carrying
conductor is proportional to
A. the square of the current
B. square of resistance
C. the current
D. inversely proportional to time
9.
The value of Joule’s mechanical equivalent of heat, J, is equal to
A. 4.2 calories per Joule
B. 2.4 Joules per calorie
C. 4.2 Joules per calorie
D. 4.2 Joules
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CURRENT ELECTRICITY
10. Temperature coefficient of a conductor is defined as the
A.
B.
C.
D.
increase in resistance per ohm per degree centigrade
increase in resistance per degree centigrade
increase in resistance per degree absolute
decrease in resistance per ohm per degree centigrade
11. When current flows in a conductor, heat is produced because
A.
B.
C.
D.
heat α I2
of electronic collision
of interatomic collision
of Joule’s law
12. Heating effect of current has undesirable side effect in
A.
electric oven
B.
electric iron
C.
immersion heater
D. vacuum cleaner
13. The resistance of carbon (filament in carbon-filament lamps) when its temperature is decreased
A. increases
C. remains the same
B. decreases
D. increases enormously
14. The curve representing Ohm’s law is
A.
a parabola
B. linear
C. sine function
D. a hyperbola
15. The condition in Ohm’s law is that
A.
B.
C.
D.
ratio V/I should be constant
current should be proportional to voltage
the temperature should remain constant
the temperature should vary
16. Ohm’s law does not apply to
A.
B.
C.
D.
conductors
conductors when there is change in temperature
semiconductor
a.c. circuit
17. Ohm’s law is applicable to
A.
C.
electric arc
gas discharge lamps
B. rectifying devices
D. none of these
18. Ohm’s law can be applied with certain reservations to
A.
C.
rectifying devices
electrolytes
B. semiconductors
D. thermionic valves
19. The presence of an electric current is made known by
A.
C.
flashing
cracking
B. effects produced
D. electric shock
20. An electric current can neither be
A. felt, seen
C. seen, produced any effect
nor
.
B. seen, touched
D. produced, felt
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CURRENT ELECTRICITY
21. The presence of the current is only made known by the effect it produces. Three important effects
are
A.
B.
C.
D.
heating, electric shock and generation
generation, chemical and electric shock
heating, magnetic and electric shock
heating, magnetic and chemical
22. Voltage applied across a circuit, acts as
A. mass of electrons
C. a component of current
B. negative ions
D. a force
23. In a series circuit the current is
A. constant
C. proportional to the resistance
B. always zero
D. different in different resistors
24. In a parallel circuit the potential difference across the resistance
A.
C.
varies
is sometimes constant
B. is different from the applied voltage
D. is always constant
25. The resistance R1 and R2 are connected in parallel. The ratio of values of resistance R1 : R2 is 4 :
1. The currents in R1 : R2 will be equal to
A. 1 : 4
B. 1 : 1
C.
4:1
D.
4:4
26. A resistance of 4 ohms is connected across 100 V supply. When another resistor ‘R’ ohms is
connected in parallel with 4 ohms, the total current taken from supply was found to be 50 A. The
value of resistance ‘R’ is
A. 2 ohms
B. 3 ohms
C. 5 ohms
D. 4 ohms
27. The voltage applied across an electric press was reduced by 50%. The power consumed by the press
will be reduced by
A. 25%
B. 75%
C. 60%
D. 50%
28. Two electric presses are connected in parallel. The resistance of the first press is 100 ohms and
that of the second is 300 ohms. The total current taken by both the presses is 4 A. The ratio of
current taken by first : second will be equal to
A. 2 : 3
B. 1 : 3
C. 3 : 1
D. 1.2 : 3
29. Three elements having conductance G1, G2 and G3 are connected in parallel. Their combined
conductance will be
A.
G1 + G2 + G3
C.
G1G2 + G2G3 + G3G1
G1 + G2 + G3
B.
1
D.
1
G1
G2
G3
30. Four resistances R1, R2, R3 and R4 are connected in series against 220 V supply. The resistances
are such that R1 > R2 > R3 > R4. The least power consumption will be in
A. resistor R1
B. resistor R4
C. resistor R3
D. resistor R2
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CURRENT ELECTRICITY
31. When current flows through heater coil it glows but supply wiring does not glow because
A.
B.
C.
D.
supply wiring is covered with insulation layer
current through supply line flows at slower speed
supply wires are made of superior material
resistance of heater coil is more than that of supply wires
32. Resistors commonly used in power circuits are
A.
C.
carbon resistors
wire wound resistors
B. etched circuit resistors
D. deposited metal resistors
33. International ohm is defined in terms of resistance of
A. a column of mercury
C. unit length of metal wire
B. a cube of carbon
D. a cube of copper
34. Which of the following has negative coefficient of resistance?
A.
C.
wire wound resistor
thermistor
B. non-metals
D. metals
35. The current carrying capacity of the fuse material depends on
A. length
C. cross-sectional area
B. material
D. all of these
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MAGNETISM AND ELECTROMAGNETISM
1.
2.
3.
4.
A natural magnet is called
A. steel
B. lodestone
C.
A magnet is able to attract
A. iron, aluminum and brass
C. iron, copper and nickel
B. iron, cobalt and zinc
D. nickel, cobalt and steel
Externally, magnetic line of force travels
A. south to north
C. negative to positive
B. north to south
D. in both directions
magnetism
A material commonly used for shielding or screening magnetism is
A. brass
B. aluminum
C. copper
D. soft iron
D. soft iron
5.
The magnetism that remains in a magnet after the magnetizing force has been removed is called
A. permeability
B. induction
C. residual
D. saturation
6.
Iron becomes magnetized by induction when it is
A. heated
B. suspended east and west
C. near to one end of a magnet
D. treated with some chemicals
7.
Magnetic lines of force are called
A. hysteresis
B. current
C.
flux
D. magnetomotive force
8.
The force between two magnetic poles varies with distance between them. The variation is
A. in direct proportion to the distance
B. in inverse proportion to the distance
C. in direct proportion to the square of the distance
D. in inverse proportion to the square of the distance
9.
The magnetic potential in a magnetic circuit can be measured in terms of
A. farads
B. M.M.F.
C. coulombs
D. none of these
10. Permeance is analogous to
A.
conductance
B.
resistance
C.
reluctance
D.
none of these
11. The permeability of a material means
A.
B.
C.
D.
strength of permanent magnet
strength of an electromagnet
the magnetization left in the iron after exciting field has been removed
the conductivity of a material for magnetic lines of force
12. When the magnetic flux
(φ)
(B) can be given as
and the area (A) under its influence are known, the magnetic flux
density
A.
B = φA
B.
=φ
C.
B=A
φ
D.
B = φA 2
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MAGNETISM AND ELECTROMAGNETISM
13. The relative permeability µr is given by
A.
C.
B.
µ0
D.
µ
B
H
µ0
H
14. Relative permeability of a material is given by (K is susceptibility of the material)
A.
1 + µ0K
C.
1 + µ0
K
B.
+
C.
µ0H
15. The relative permeability of paramagnetic substance is
A.
C.
slightly less than 1
slightly greater than 1
B. equal to 1
D. very much greater than 1
16. The value of permeability for the free space is
A.
4 x 10–7 Hm–1
B. 4
x 10–7 Hm–1
C.
4π x 107 Hm–1
D.
1 × 10 − 7 Hm−1
4π
17. The magnetization in any magnetic material appears as a result of
A.
electrons orbital motion
C. spin of the nucleus about its axis
B.
electron spin
D. all of these
18. The sum of the magnetic moments in unit volume of the solid is called
A. field strength
C. permeability
B. magnetization
D. susceptibility
19. Which of the following materials does not have permanent magnetic dipole
A. paramagnetic
C. diamagnetic
B. antiferromagnetic
D. ferrimagnetic
20. Interaction between the neighboring dipoles is negligible in case of a
A. paramagnetic material
C. antiferromagnetic material
B. diamagnetic material
D. ferrimagnetic material
21. Each ferromagnetic material has characteristic temperature above which its properties are quite
different from those below that temperature. This temperature is called
A. transition temperature
B. Faraday’s temperature
C. demagnetization temperature
D. Curie temperature
22. The relative permeability µ for iron is
A.
5000
B.
7000
C. 3000
D. 1000
23. Which of the following material is used for making permanent magnets
A.
carbon steel
B.
platinum cobalt
C. Alnico V
D. All of these
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MAGNETISM AND ELECTROMAGNETISM
24. Which of the following has the highest value of relative permeability µr?
A.
iron
B. supermalloy
C.
Mu-metal
D.
4% Si – Fe
25. Ferrimagnetic materials generally behave as a
A. semiconductor
C. insulator
B. conductor
D. any of A, B, or C
26. Transformer cores operating at microwave frequency ranges are generally made up of
A.
ferrites
B.
silicon steel
C.
supermalloy
D.
alnico V
27. The magnetic materials which can be easily magnetized in both directions are known as
A.
C.
soft magnetic materials
low hysteresis loss materials
B.
D.
hard magnetic materials
high hysteresis loss materials
28. Eddy current loss can be minimized by
A.
B.
C.
D.
decreasing the resistance of magnetic medium
increasing the resistance of magnetic medium
decreasing the permeability of magnetic medium
none of the above
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ELECTROMAGNETIC INDUCTION
1.
The coefficient of self-inductance of a coil is defined as
A. NI/ φ
φ/
B.
NI
C
.
D.
φI / N
2.
Which of the following statement is incorrect?
A. Whenever the flux linking with the coil or circuit changes the emf is produced.
B. The direction of dynamically induced emf can be determined by Flemming’s right hand rule.
C. Coefficient of coupling for tightly coupled coil is zero.
D. The coefficient of self-inductance is proportional to the square of number of turns on it.
3.
Which of the following statements about inductance of a coil is true?
A. Inductance is a characteristic of coil occurring only in case of A.C.
B. Inductance appears only if the coil has an iron core.
C. Inductance is only another expression for self-induced voltage.
D. Inductance characterizes the magnetic properties of a coil which are significant for the
value of self-induced voltage generated due to current change in the coil.
4.
A collapsing field around a coil
A. tends to oppose the decay of coil current
B. helps the decay of coil current
C. tends to aid current flow reversal
D. does not affect the coil current flow
5.
Energy stored in an inductance is given by
A.
C.
6.
2LI2 joules
Nφ
joules
I
Which of the following is a vector quantity?
A. magnetic potential
C. magnetic field intensity
B.
D.
0 joule
joules
B. flux density
D. relative permeability
7.
A conductor of length L has current I passing through it, when it is placed parallel to a strong
magnetic field. The force experienced by the conductor will be
A. BLI
B. zero
C. B2LI
D. BL2I
8.
Whenever a conductor cuts magnetic flux, an emf is induced in that conductor. This statement is
due to
A. Joule’s law
B. Coulomb’s law
C. Faraday’s law
D. Weber and Ewing’s theory
9.
The left hand rule correlates
A. self induction, mutual induction and direction of force on a conductor
B. magnetic field, electric field and direction of force on a conductor
C. current, induced emf and direction of force on a conductor
D. current, magnetic field and direction of force on a conductor
10. In the left hand rule, thumb always represents
A. voltage
C. direction of force on conductor
B. current
D. magnetic field
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ELECTROMAGNETIC INDUCTION
11. The coefficient of coupling between two air core coils depends on
A.
B.
C.
D.
self inductance of the two coils only
mutual inductance between the two coils only
mutual inductance and self inductance of the two coils
none of the above
12. While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which
parameter of electric circuit?
A. e.m.f.
C. conductivity
B. current density
D. current
13. While comparing magnetic and electric circuits, the point of dissimilarity exists while considering
A. flux and current flow
C. m.m.f. and e.m.f.
B. permeance and conductance
D. reluctance and resistance
14. The effect of the inductance of a coil on a constant direct current is that
A.
B.
C.
D.
it strengthens the current
it does not affect the constant direct current
it decreases the current
it causes a higher voltage drop
15. Good smoothing factor of a coil depends on the
A. terminal voltage
C. inductance of the coil
B. property of the wire of the coil
D. cross-sectional area of the wire of the coil
16. Leakage factor is
A. less than unity
C. more than unity
B. equal to unity
D. zero
17. The law that induces emf and current always opposes the cause producing them was discovered by
A. Lenz
C. Maxwell
B. Faraday
D. Ohm
18. According to Lenz’s law the direction of induced e.m.f. and hence current
A.
B.
C.
D.
may be found by the right hand rule
always opposes the cause producing it
is determined by the rate of cutting flux
may be found by the left hand rule
19. Sparking occurs when a load is switched off because the circuit has high
A. capacitance
B. inductance
C. resistance
20. The flux linked with a coil of inductance L carrying current i
is
A. True
B. False
C.
D. impedance
d
dt
Partly true
(Li )
D. Partly false
21. When steel toroidal ring is magnetized by passing current through its coil, it develops no magnetic
poles
A. True
B.
False
C.
Partly true
D.
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Partly false
ELECTROMAGNETIC INDUCTION
22. Air gap in the iron core of an inductor prevents
A. hysteresis loss
C. transformer action
B. flux change
D. core saturation
23. The growth of current in an inductive circuit follows
A. hyperbolic law
C. exponential law
B. Ohm’s law
D. linear law
24. The time constant of an inductive circuit is defined as the ratio of
A. R/L
B.
Rt/L
C.
Lt/R
D. L/R
25. The time constant is the time it takes the current in an inductive circuit to rise to
A.
B.
C.
D.
66% of its final steady state value
70% of its final steady state value
63% of its final steady state value
50% of its final steady state value
26. Mutual inductance can also be defined as:
A.
=
B.
M = N2
D.
M=N
dt
φ
C.
M=N
di
2 dt
2 dφ
27. The mutual inductance of two coils is maximum when the coils are
A.
B.
C.
D.
inclined at an angle of 45 degrees
at right angle to each other
facing each other
touching each other
28. The value of mutual inductance in terms of self inductance of the two coils L 1 and L2 is
proportional to
A.
C.
B.
L1L
2
L1 L2
L
1
L
2
D.
29. Coupling coefficient k, a term much used in radio work can be obtained from
A.
K=M
C.
=
L1L2
B.
K = M L1 / L 2
D.
K = ML1L 2
30. The coupling coefficient denotes
A.
B.
C.
D.
the degree of magnetic linkage
whether the reluctance remains constant
the variation of inductance between the two coils
whether the flux linkage is constant
31. It is difficult to magnetize steel because of its
A. low permeability
C. high permeability
B.
D.
high retentivity
high density
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ELECTROMAGNETIC INDUCTION
32. In electrical machines, laminated cores are used with a view of reducing
A. eddy current loss
C. hysteresis loss
B. copper loss
D. windage loss
33. The area of hysteresis loop represents hysteresis loss in
A. J/m3/s
C. J/s
B. J/cycle
D. J/m3
34. According to Hysteresis law, hysteresis loss in a material is proportional to
A. B1.2
C. B0.6
B. B1.6
D. B3.6
35. A degaussing is the process of
A.
B.
C.
D.
removing gases from materials
removal of magnetic impurities
demagnetizing metallic part
magnetizing nonmetallic part
36. Hysteresis losses can be reduced by
A.
B.
C.
D.
using grain-oriented silicon steel
increasing the frequency of the field
laminating the core
none of these
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ELECTROSTATICS
1.
Absolute permittivity of vacuum is taken as
A. 8.854 x 10–6 farad/meter
B. 8.854 x 10–12 farad/meter
C. 8.854 x 10–9 farad/meter
D. 8.854 x 1012 farad/meter
2.
Relative permittivity of vacuum is
A. zero
C. unity
B. 8.854 x 10–6 farad/meter
D. 9 x 109 farad/meter
3.
In the electric field, the potential is the work done in joules
A. to bring positive charge of one coulomb from infinity to that point
B. to bring any charge from infinity to that point
C. in moving a unit positive charge from one point to the other point
D. to bring any charge from any point to infinity
4.
The unit of field intensity is
A. coulomb
C. newtons/coulomb
B. coulomb/m2
D. newtons/m2
5.
Coulomb’s law for the force between electric charges most closely resembles with
A. Gauss theorem
B. Newton’s law of gravitation
C. Law of conservation of energy
D. Newton’s laws of motion
6.
Which of the following equations is correct?
A. ∫E d l = 0
q
C. ∫ Ed s =
ε0
7.
8.
9.
The
field
A.
C.
B.
D.
→
F = yi + x j is a
rotational field
conservative field
Dielectric strength of a material depends on
A. moisture content
C. temperature
B.
D.
irrotational field
static electric field
B. thickness
D. all of these
What will happen to an insulating medium if voltage more than the breakdown voltage is applied?
A. it will get punctured
B. it will become magnetic
C. it will melt
D. its molecular structure will change
10. Which medium has the highest value of dielectric strength?
A. glass
C. porcelain
B. mica
D. quartz
11. The maximum value of potential gradient in a cable occurs in
A.
B.
outer sheath
conductor
B. insulation
D. uniformly all over
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ELECTROSTATICS
12. A region around a stationary electric charge has
A. electric field
C. both electric and magnetic field
B. magnetic field
D. neither of the two
13. Inside a hollow spherical conductor
A.
B.
C.
D.
electric field is constant
electric field is zero
electric field changes with distance from the center of the sphere
electric field is unity
14. Capacitors are said to
A.
C.
block a.c. and pass d.c.
pass a.c. and d.c.
B. block d.c. and pass a.c.
D. block a.c. and d.c.
15. Which statement influences the capacity of a capacitor?
A.
B.
C.
D.
area of the plates, thickness of the plates and the rate of charge
area of the plates, dielectric and the rate of charge
distance between the plates, dielectric and thickness of the plates
distance between the plates, area of the plates and dielectric
16. The effect of the dielectric is to
A.
C.
increase the capacitance
reduce the working voltage
B. decrease the capacitance
D. increase the distance between the plates
17. Electrolytic capacitor is the most commonly used type but it has two disadvantages, namely
A.
B.
C.
D.
low insulation resistance and suitable for d.c. only
high insulation resistance and suitable for a.c. only
high capacitance and high insulation resistance
high capacitance and low insulation resistance
18. In a radio, a gang condenser is a type of
A.
air capacitor
B.
paper capacitor
C. ceramic capacitor
D.
electrolytic capacitor
19. A sphere of one meter radius can attain a maximum potential of
A.
1000 V
B.
3 million volts
C. 30 kV
D. 3 kV
20. The power dissipated in a pure capacitor is
A. maximum
C. zero
B. minimum
D. depends on the size and voltage
21. One farad is
A. coulomb–joule
C. joule per volt
B. one coulomb per volt
D. one volt per coulomb
22. If a dielectric is placed in a electric field, the field strength
A. decreases
C. remains the same
B. increases
D. becomes zero
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ELECTROSTATICS
23. If the medium of a parallel-plate capacitor consists of mica and air, the capacitance is increased by
A.
B.
C.
D.
increasing the air space
increasing the area of the plates
decreasing the area of the plates
increasing the thickness of mica
24. A capacitance C is charged through a resistance R. The time constant of the charging circuit is given
by
A.
RC
B.
1
C
C
R
D.
R
C
.
RC
25. A circuit component that opposes the change in the circuit voltage is
A.
resistance
B.
inductance
C.
capacitance
D. none of these
26. In a capacitor, the electric charge is stored in
A.
C.
metal plates
dielectric as well as metal plates
B. dielectric
D. neither dielectric nor metal plates
27. Internal heating of a capacitor is usually attributed to
A. leakage resistance
C. plate vibration
B. electron movement
D. dielectric charge
28. The ohmmeter reading for a shorted capacitor is
A.
infinity
B.
few kilo ohms
C.
few mega ohms
D. zero
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ELECTROLYSIS AND STORAGE BATTERIES
1.
Electrochemical equivalent is
A. ratio of atomic weight of an element to atomic weight of hydrogen
B. mass of the element liberated per unit quantity of hydrogen
C. ratio of atomic weight of valency
D. none of the above
2.
The mass of material deposited over an electrode is
A. proportional to voltage
B. proportional to time only
C. proportional to current only
D. proportional to quantity of electricity and electrochemical equivalent
3.
The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity
which passes through the electrolyte. The above statement is associated with
A. Gauss’s theorem
B. Laplace law
C. Weber and Ewing’s theory
D. laws of electrolysis
4.
In electroplating, the positive electrode is called the
A. cathode
B. anode
C. terminal
D.
iontrap
5.
Impurities in an electrolyte can cause an internal short circuit condition called
A. depolarization B. electrolysis
C. local action
D. polarization
6.
Distilled or approved water is used in electrolytes because it
A. prevents or slows down local action
B. speeds up electrochemical action
C. improves specific gravity
D. prevents polarization
7.
The condition of a liquid electrolyte is measured in terms of its
A. current value B. specific gravity
C. acid content
D. voltage output
8.
One factor affecting voltages of the primary cell is the
A. area of the plates
B. distance between the plates
C. types of plates and electrolyte
D. thickness of the plates
9.
Local action in the primary cell can be rectified by
A. charging the cell
B. amalgamating the zinc electrode with mercury
C. using the cell for just few minutes
D. dry cell
10. The action of a dry cell is to change
A.
B.
C.
D.
chemical action to mechanical energy
chemical action to electrical energy
electrical energy into mechanical energy
electrical energy into magnetic energy
11. Polarization in dry cell can be got rid of by
A.
C.
coating the electrodes of the cell
discharging the cell
B. chemical means
D. disposing the cell
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ELECTROLYSIS AND STORAGE BATTERIES
12. The two main defects of the primary cell are
A.
C.
polarization and sulphation
buckling and polarization
B. local action and polarization
D. sulphation and buckling
13. The average dry cell gives an approximate voltage of
A.
1.3 V
B. 1.5 V
C.
1.1 V
D. 1.7 V
14. To obtain a high voltage of about 1.9 V from a dry cell, one would use
A.
C.
Western standard cell
Nickel cadmium cell
B. Leclanche cell
D. Magnesium cell
15. When n cells, each of emf E volts, and internal resistance r ohms are connected in series, the
current i through an external resistance R ohms is given by
A.
B. i = E
E
i
n
C.
D.
i
=
r + nR
16. When n cells, each of emf E volts, and internal resistance r ohms are connected in parallel, the
strength of the current i is given by
A.
B.
nE
r+
R
D.
E
+
C.
E
n + Rr
R+n
r
17. Cells are connected in parallel to
A.
C.
increase the internal resistance
increase the current capacity
B. decrease the current capacity
D. increase the voltage output
18. Cells are connected in series to
A. decrease the voltage output
C. decrease the internal resistance
B. increase the voltage output
D. increase the current capacity
19. The function of the depolarizer in carbon zinc cell is that
A.
B.
C.
D.
it converts the produced hydrogen into water
it prevents the fast chemical action on the zinc container
it synthesizes the decomposed electrolyte
it absorbs the oxygen produced in the cell
20. Which of the following acts as depolarizer in dry cell?
A. manganese dioxide
C. ammonium chloride
B. zinc chloride
D. carbon powder
21. One advantage of a secondary cell is that it
A. can be recharged
C. it is compact, easy to carry
B. can be used for portable equipment
D. cannot be recharged
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ELECTROLYSIS AND STORAGE BATTERIES
22. The composition of a secondary cell is
A.
B.
C.
D.
zinc, copper and dilute sulphuric acid
zinc, carbon and dilute sulphuric acid
lead, lead peroxide and dilute sulphuric acid
zinc, copper and dilute boric acid
23. Nickel-cadmium dry cell is becoming popular in power supplies to electronic calculators because
A.
C.
it has a standard shape
it is rechargeable
B. it is dry
D. it is easily manufactured
24. Secondary cell can produce large amounts of power for a
A.
B.
C.
D.
short time and can be recharged
long time and can be recharged
short time and cannot be recharged
long time and cannot be recharged
25. Gassing occurs in the process of
A. charging an accumulator
C. discharging an accumulator
B. charging a dry cell
D. discharging a dry cell
26. The condition of a secondary cell can be determined by
A.
B.
C.
D.
its terminal voltage
the color of the electrolyte
the level of the electrolyte
the terminal voltage and strength of the electrolyte
27. The lead acid accumulator should be recharged when the specific gravity of the electrolyte is about
A.
1.15
B.
1.80
C.
1.25
D. 1.35
28. Other types of accumulators besides the lead acid type are
A.
C.
alkaline batteries only
alkaline and dry batteries
B. alkaline and solar batteries
D. nickel-cadmium batteries
29. Electrolyte of a storage battery is formed by adding
A. water to hydrochloric acid
C. hydrochloric acid to water
B. sulphuric acid to water
D. water to sulphuric acid
30. When the electrolyte of a storage battery is low it is usually proper to
A.
B.
C.
D.
add a special weak acid solution
top up with distilled water
charge the battery for a short time before adding an electrolyte
drain the battery completely and fill it with fresh electrolyte
31. The ampere hour capacity of battery depends on
A. the thickness of the plates
C. the strength of the electrolytes
B. the area of the plates
D. the distance between the plates
32. To keep the terminals of a lead acid storage battery free from corrosion, it is advisable to
A.
C.
clean the terminals frequently
keep the electrolyte level low
B. charge for battery at frequent intervals
D. apply petroleum jelly
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ELECTROLYSIS AND STORAGE BATTERIES
33. The internal resistance of a discharged battery compared with a charged one
A.
C.
is more
remains the same
B. is less
D. is negative
34. It is not desirable to leave a lead storage battery in a discharged state for a long time mainly
because
A. electrolyte will attack the container
C. electrolyte will become weak
B. plates will become sulphated
D. acid will evaporate
35. A partially discharged lead storage battery may be brought back to full charge by
A.
C.
adding sulphuric acid
B. adding distilled water
applying ac voltage across the terminals D. applying dc voltage across the terminals
36. Which of the following is a primary cell
A. mercury oxide
C. nickel-iron-alkaline
B.
D.
lead-acid
nickel-cadmium-alkaline
37. Charging a lead-acid cell causes the electrolyte to become
A.
stronger
B.
stable
C.
weaker
D.
water
38. Separators in storage battery cell are designed to prevent the plates from
A.
C.
touching the electrolyte
shorting together
B. touching the container
D. shorting to the sediment
39. Which of the following affects the capacity of a lead-acid battery?
A.
temperature
B.
discharge time
C.
specific gravity
D. all of these
40. During the charging period of a lead-acid battery, the charging rate is lowered to prevent violent
gassing because
A. the gasses given off are explosive
B. evaporation of the electrolyte will weaken its effect
C. the cells will be subjected to excessive pressure
D. violent gassing tends to wash the active material from the plates
41. A fuel cell converts
A.
mechanical
B.
energy into electrical energy.
magnetic
C. chemical
D. solar
42. A cell which is used as voltage reference source for instrument calibration is
A. solar cell
C. mercury-cadmium cell
B. dry cell
D. nickel-cadmium cell
43. The advantage of the iron-nickel battery over the lead-acid battery is that
A.
B.
C.
D.
it has a much higher efficiency
it needs less maintenance
the cell voltage of the iron-nickel battery is higher
it is much cheaper
44. While charging accumulators, one should
A.
B.
C.
D.
check the acid level with a lighted match
short the cells to see if they are full charged
keep them in a well-ventilated space
connect and disconnect them with the supply on
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D.C. GENERATORS
1.
The output voltage of a single loop generator is a
A. steady d.c.
B. steady a.c.
C.
pulsating a.c.
2.
A smooth output from a generator is obtained by
A. design of the armature winding
B. changing the form of the commutator
C. changing the field strength
D. design of the commutator
3.
The output voltage of a generator is given by the equation
dφ
E = −L di
D. E = N
dt
dt
What effect on current flow does reversing the direction of movement of a conductor in the
magnetic field of a generator have
A. neutralizes the current flow
B. has no effect on current
C. it reverses the direction of current flow
D. has no effect on the voltage
A.
4.
D. pulsating d.c.
E = V − IaR
a
B.
=
+
C.
5.
In most generators the output voltage is induced by
A. rotating magnetic field past stationary coils
B. relative motion between the field and the armature coils
C. converting electrical energy into mechanical energy
D. converting chemical energy into electrical energy
6.
How would you determine, from visual observation of the armature winding, whether a generator is
lap or wave wound
A. connection to the field winding
B. connection to the commutator
C. connection to the brushes
D. the direction of the end connection
7.
What classification is given to a d.c. generator that receives its field excitation current from
internal source?
A. self excited
B. controlled excitation
C. separately excited
D. internally excited
8.
The shunt field of a compound generator is connected across both the series field and the
armature. This connection is known as
A. short shunt
B. long shunt
C. differential compound
D. cumulative compound
9.
For all symbols having their usual meaning, the emf generated in the lap winding is given by
B. E = φZNA
2P
A.
D.
C.
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D.C. GENERATORS
10. Residual magnetism is necessary in a
A. separately excited generator
C. both of these
B. self excited generator
D. none of these
11. If the number of poles in a lap wounded generator is increased by a factor of 2, the generated emf
will
A. remain the same
C. decrease by a factor of 2
B.
D.
increase by a factor of 2
increase by a factor of 4
12. Electric dc generators have normally, an overall efficiency of the order of
A. 60-80%
B.
75-85%
C. 80-90%
D. 85-95%
13. The armature magnetic field has effect that
A.
B.
C.
D.
it demagnetizes or weakens the main flux
it cross magnetizes, or distorts it
it magnetizes or strengthens the main flux
A and B
14. Brushes are always placed along
A. magnetic neutral axis (MNA)
C. perpendicular to MNA
B. geometric neutral axis (GNA)
D. perpendicular to GNA
15. Magnetic neutral axis makes an angle of
A. 0o
B. 90o
C.
16. In a dc generator, the flux is seen to be
the leading pole tips.
A. weakened, weakened
C. crowded, weakened
with the flux passing through the armature.
45o
D. 180o
at the trailing pole tips and also
at
B. weakened, crowded
D. same, same
17. If Өm is the forward lead angle in radians, Z is the total number of conductors and I is the current
in each armature pole, the demagnetizing ampere-turns/pole are given as
A.
C.
AT = ZI × θm
180
a
(1
−
AT
a
B.
=
×
D.
none of these
18. The function of a compensating winding is to neutralize the
A.
B.
C.
D.
reactance voltage generated as a consequence of commutation
cross magnetize the effect of armature reaction
demagnetizing effect of armature reaction
all of these
19. In the commutation process it is the
A.
B.
C.
D.
current which is getting reversed
voltage which is getting reversed
both of these
none of these
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D.C. GENERATORS
20. In any dc generator the emf generated in the armature is maximum when
A.
B.
C.
D.
rate of change of flux linked is minimum
rate of change of flux is maximum
flux linked with conductor is maximum
flux linked with conductor is minimum
21. A simple method of increasing the voltage of a dc generator is
A.
B.
C.
D.
to decrease the air gap flux density
to increase the speed of rotation
to decrease the speed of rotation
to increase the length of the armature
22. The method which can be used to improve commutation process is
A. increasing the resistance of the brushes
B. reducing the number of turns in the armature coil and hence the number of segments in the
commutator
C. to neutralize the reactance voltage by producing a reverse emf in the short circuit coil
under commutation
D. all of the above
23. The function of interpole or compole is
A.
B.
C.
D.
to neutralize the reactance voltage and help in commutation process
to neutralize the cross-magnetizing effect of armature reaction
to neutralize the demagnetizing effect of the armature
A and B
24. Interpoles are connected in
with the armature and compensating windings are connected in
with the armature.
A. series, series B.
series, shunt
C.
shunt, series
D. shunt, shunt
25. The function of an equalizer ring is
A.
B.
C.
D.
to avoid unequal distribution of current at the brushes
to help to get sparkless commutation
both of these
none of these
26. Generators are often preferred to be run in parallel because of having the advantages of
A. great reliability
C. meeting greater load demand
B. generator efficiency
D. all of the above
27. Which of the following is most suitable for running in parallel operation?
A. shunt generator
C. compound generator
B. series generator
D. all of these are equally suitable
28. Critical resistance of a dc generator Rc
A. Rc α (speed)–1
C. Rc α (speed)2
B. Rc α (speed)
D. Rc α (speed)–2
29. Shunt generators are used where the main requirement is a constant
A. current and voltage
C. voltage over a wide load range
B. current
D. voltage over a narrow load range
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D.C. GENERATORS
30. Equalizer connections are required when paralleling two
A. compound generators
C. shunt generators
B.
C.
series generators
long shunt generators
31. The function of an interpole is
A.
B.
C.
D.
neutralize cross-field of armature reaction and obtain ideal commutation
increase the armature reaction and thus obtain ideal commutation
neutralize cross field of the armature reaction and thus obtain under commutation
increase the armature reaction and thus obtain over commutation
32. Interpoles are normally connected in
A. parallel with field
C. parallel with the load
B. series with the field
D. series with the load
33. In DC generators, lap winding is used for
A. low voltage, low current
C. low voltage, high current
B. high voltage, high current
D. high voltage, low current
34. DC generators preferred for charging automobile batteries is
A. shunt generator
C. long shunt compound generator
B. series generator
D. short shunt generator
35. Which of the following component of a dc generator plays vital role for providing direct current of
a dc generator?
A. dummy coils
B.
equalizer rings
C.
eye bolt
D. commutator
36. In dc generator the ripples in the direct emf and generated are reduced by
A.
B.
C.
D.
using equalizer rings
using commutator with large number of segments
using carbon brushes of superior quality
using carbon brushes of excellent quality
37. Which of the following generators are preferred for parallel
A. series generator
C. compound generator
operations?
B. shunt generator
D. all of the above
38. Full load efficiency of the generator will be
A. 68.5%
B.
73.5%
C. 80.8%
D. 92.51%
C.
D. windage loss
39. Which loss in dc generator varies with load
A. copper loss
B.
eddy current loss
hysteresis loss
40. In dc generator, the cause of rapid brush wear may be
A. imperfect contact
C. rough commutator surface
B. sever sparking
D. any of the above
41. In a shunt generator, the voltage built up generally restricted by
A. speed limitation B.
armature heating
C.
saturation of iron D.
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brush wear
D.C. GENERATORS
42. The armature of a dc generator is laminated to
A. reduce the bulk
C. reduce eddy current loss
B. insulate the core
D. provide passage for cooling air
43. Which of the following helps in reducing the effect of armature reaction in dc generator?
A. compensating windings
C. both A and B
B. interpoles
D. neither A nor B
44. With dc generator, which of the following regulation is preferred
A. 1% regulation
C. infinite regulation
B.
D.
50% regulation
100% regulation
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D.C. MOTORS
1.
What is the effect produced by the electric motor?
A. magnetic effect only
B. magnetic as well as heating effect
C. heating effect only
D. heating as well as chemical effect
2.
The rotating part of a dc motor is know as
A. pole
B. stator
C. armature
3.
The function of the commutator in a dc machine is
A. to change alternating current to direct current
B. to improve commutation
C. for easy speed control
D. to change alternating voltage to direct voltage
4.
Carbon brushes are used in electric motors to
A. brush off carbon deposits on the commutator
B. provide a path for flow of current
C. prevent overheating of armature windings
D. prevent sparking during commutation
5.
Voltage equation for dc motor is
A. V = Eb + IaRa B.
V = Eb – IaRa
6.
C.
Eb = V + IaRa
D. carbon brush
D. Eb = V – IaRa
Condition for maximum power output for a dc motor is
A. Eb = V
B. Eb = V/2
C.
Eb = IaRa
D. Eb =
7.
The speed of a dc motor is
A. directly proportional to back emf and inversely proportional to flux
B. inversely proportional to back emf and directly proportional to flux
C. directly proportional to emf as well as flux
D. inversely proportional to emf as well as flux
8.
The highest speed attained by a dc shunt motor is
A. equal to infinity of rated flux
B. higher than no load speed at rated flux
C. equal to no load speed at rated flux
D. lower than no load speed at rated flux
9.
In a dc motor iron losses occur in
A. the yoke
B. the armature
C.
the field
2
IaRa
D. none of these
10. The dummy coil in dc machines is used to
A.
B.
C.
D.
1
eliminate reactance voltage
eliminate armature reaction
bring about mechanical balance of armature
eliminate harmonics developed in the machine
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D.C. MOTORS
11. An external resistance is added in the series with the field of a dc shunt motor. When the motor
runs, the effect of resistance is
A. to reduce the speed of the motor
B. to increase the speed of the motor
C. to reduce the armature current drawn by the motor
D. to reduce the losses
12. The speed of a dc shunt motor is required to be more than F.L. speed. This is possible by
A.
B.
C.
D.
increasing the armature
decreasing the armature current
increasing the excitation current
reducing the field current
13. If speed of a dc shunt motor increases, the back emf
A. increases
C. remains constant
B. decreases
D. decreases and then increases
14. The current flowing in the conductors of a dc motor is
A. ac
B.
dc
C. ac as well as dc
D. transients
15. As the load is increased the speed of a dc shunt motor will
A. remain constant
C.
B.
increase
proportionately
D. reduce slightly
increase slightly
16. The current drawn by armature of a dc motor is
A.
V
Ra
B.
Eb
Ra
D.
C.
Eb − V
Ra
17. If the current in the armature of a dc series motor is reduced to 5%, the torque of the motor will
become
A. 50% of the previous value
B. 25% of the previous value
C. 150% of the previous value
D. 125% of the previous value
18. The shunt current flowing in short shunt compound-wound motor is given by
I
= V − Isc R
A. I
= V
B.
=
D. none of these
C.
sh
R
sh
sc
sh
R sh
19. In dc shunt motor, if the terminal voltage is reduced to half and torque remains the same, then
A.
B.
C.
D.
speed will be half and armature current also will be half
speed will be half and armature current remains the same
speed will be half and armature current becomes double
speed and armature current will remain the same
20. One dc motor drives another dc motor. The second dc motor when excited and driven
A. runs
D. runs as a generator
B. does not run as a generator
D. also runs as a motor
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D.C. MOTORS
21. Armature torque of a dc motor is given by
A.
C.
-m
=
N-m
B.
T = 0.16
D.
T=P
A kg-m
-m
22. The torque of a motor is
A.
B.
C.
D.
the force in N-m acting on the rotor
the product of tangential force on the rotor and its radius
the electrical power in kW
the power given to load being driven by the motor
23. The armature current drawn by any dc motor is proportional to
A. the voltage applied to the motor
C. the flux required in the motor
B. the torque required
D. the speed of the motor
24. The output power of any electrical motor is taken from
A. the armature
C. the conductors
B. the coupling mounted on the shaft
D. the poles
25. The power stated on the name plate of any motor is always
A. the output power of the shaft
C. the power drawn in kW
B. the power drawn in kVA
D. the gross power
26. A starter is necessary to start a dc motor because
A. it starts the motor
C. it limits the back emf to a safe value
B. it limits the speed of the motor
D. it limits the starting current to safe value
27. The efficiency of any electrical machine/apparatus will be high, if
A. its losses are minimum
C. voltage applied is constant
B. its losses are more
D. the current drawn is minimum
28. The direction of rotation of a dc motor is reversed by
A. reversing armature connections
C. adding resistance to the field circuit
29. The armature of dc motor is
laminated
to reduce the hysteresis losses
C. to reduce the inductivity of armature
B. interchanging the armature and field
D. connection
reversing supply connection
B. to reduce the eddy current losses
A.
D. to reduce the mass of the armature
30. Which of the following is a correct statement about a series motor?
A.
B.
C.
D.
its field winding consists of thicker wire and less turns
it can run easily without a load
it has an almost constant speed
it has a poor torque
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D.C. MOTORS
31. Which of the following dc motors has the least drop in speed between no load and nominal load?
A.
B.
C.
D.
shunt motor with commutating poles
series motor without commutating poles
compound motor without commutating poles
series motor with commutating poles
32. The speed of a series motor at no load is
A.
zero
B.
3000 rpm
C.
3600 rpm
D. infinity
33. The speed of dc series motor decreases if the flux in the field winding
A.
C.
remains constant
decreases
B. increases
D. none of these
34. Which of the following motors is used to derive the constant speed line shafting lathes, blowers and
fans?
A. DC shunt motor
C. cumulative compound motor
B. DC series motor
D. differential compound motor
35. If the back emf in a dc motor is absent, then
A.
C.
motor will run at very high speed
motor will not run at all
B. motor will run at very low speed
D. motor will burn
36. The field flux of a dc motor can be controlled to achieve
A.
B.
C.
D.
the speeds lower than rated speed
the speeds higher than rated speed
the speeds at rated speed
none of these
37. By providing a variable resistance across the series field (diverter) in a dc series motor, speeds
above normal can be obtained because
A. armature current decreases
C. line current decreased
B. flux is reduced
D. none of these
38. DC series motors are best suited for traction work because
A.
B.
C.
D.
torque is proportional to the square of armature current and speed is inversely
proportional to torque.
torque is proportional to the square of armature current and speed is proportional to
torque.
torque and speed is proportional to the square of armature current.
none of these
39. A series motor is started without load. The effect is that
A. the torque increases rapidly
C. the current drawn increases rapidly
B. the speed increase rapidly
D. the back emf decreases
40. The direction of rotation of a dc series motor can be reversed by interchanging
A. the supply terminals only
C. the supply as well as field terminals
B. the field terminals only
D. none of these
41. The motor used for intermittent, high torque is
A. dc shunt motor
C. differential compound motor
B. dc series motor
D. cumulative compound motor
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D.C. MOTORS
42. If the field of a dc shunt motor is opened
A.
B.
C.
D.
it will continue to run at its rated speed
the speed of the motor will become very high
the motor will stop
the speed of the motor will decrease
43. Which of the following motors is used for rolling mills?
A.
C.
DC shunt motor
DC series motor
B. DC cumulative compound motor
D. DC differential compound motor
44. Armature reaction is attributed to
A.
B.
C.
D.
the effect of magnetic field set-up by the armature current
the effect of magnetic field set-up by the field current
copper loss in the armature
the effect of magnetic field set-up by back emf
45. What will happen if the supply terminals of a dc shunt motor are interchanged?
A.
B.
C.
D.
Motor will stop
Motor will run at its normal speed in the same direction as it was running
The direction of rotation will reverse
Motor will run at a speed lower than the normal speed in the same direction
46. When the electric train is moving down a hill the dc motor acts as
A. dc series motor
C. dc series generator
B.
D.
dc shunt motor
dc shunt generator
47. Which of the following motors is suitable for high starting torque?
A. shunt motor
C. series motor
B.
D.
cumulative compound motor
compound motor
48. For which of the following dc motors is the typical field of application mentioned?
A.
B.
C.
D.
shunt motor : electric trains
series motor : machine tools
series motor : belt drive
compound motor : fly wheel drive
49. Why is the air gap between stator and armature of an electric motor kept as small as possible?
A. to get a stronger magnetic field
C. to reach a higher speed of rotation
B. to make the rotation easier
D. to improve the air circulation
50. Interpoles are meant for
A.
B.
C.
D.
increasing the speed of the motor
decreasing the counter emf
reducing sparking at the commutator
converting armature current to dc
51. Which of the following methods is most economical for finding the no-load losses of a large dc shunt
motor is
A. Hopkinson’s test
C. retardation test
B.
D.
Swinburne’s test
none of these
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D.C. MOTORS
52. The rated speed of a given dc shunt motor is 1050 rpm. To run this machine at 1200 rpm. Which of
the following speed control scheme will be used?
A. armature current resistance control
B. field resistance control
C. Ward-Leonard control
D. none of these
53. It is preferable to start a dc series motor with some mechanical load on it because
A.
B.
C.
D.
it will not run at no load
it acts as a starter to the motor
it may develop excessive speed and damage itself
none of these
54. If the flux of a dc motor approaches zero, its speed will approach
A.
B.
C.
D.
infinity
zero
a stable value nearer to the rated speed
unity
55. A 230 V dc series motor is connected to 230 V ac. It will
A.
C.
run slowly
run with less efficiency
B. not run at all
D. run faster than its rated speed
56. The main function of a commutator in a dc motor is to
A. prevent sparking
C. reduce friction
B. convert ac to dc
D. convert dc to ac
57. Which of the following statements is incorrect? If a starter is not used with large dc motor, it will
draw a starting current which
A. is many times its full-load current
B. will produce excessive line voltage drop
C. will damage the commutator
D. will produce very slow starting torque
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A.C. FUNDAMENTALS
1.
When using circuit laws and rules we must use
A. maximum value
C. average value
B. effective value
D. peak to peak value
2.
A 60 Hz frequency would cause an electric light to
A. turn on and off 120 times per second
B. flicker noticeable
C. turn on and off 180 times per second
D. turn on and off 60 times per second
3.
The relationship between frequency f, number of revolutions per second N and pair of poles P is
given by
A. f = n/p
B. f = n/2p
C. f = np
D. f = 2np
4.
The difference between peak +ve value and the peak –ve value of an a.c. voltage is called
A. maximum value
B. average value
C. effective value
D. peak to peak value
5.
The greatest value attained during one half of the cycle is called
A. peak value
B. average value
C. rms value
D.
effective value
6.
The root mean square (r.m.s) value of an a.c. is the same as
A. instantaneous value
B. effective value
C. average value
D. maximum value
7.
The rms value of a sine wave is equal to
A. 0.637 max. value
C. 0.506 max. value
B. 0.707 max. value
D. 1.414 max. value
Form factor is defined as
A. rms value/peak value
C. rms value/average value
B. max. value/rms value
D. effective value/rms value
8.
9.
The value of form factor for a pure sine wave is
A. 1.414
B. 0.707
C.
0.637
D. 1.11
C. 0.637
D. 1.11
10. The value of peak factor for a pure sine wave is
A.
1.414
B.
0.707
11. If the current and voltage are out of phase by 90 degrees, the power is
A.
1.1 V.I.
B.
maximum
C. minimum
D. zero
12. If e1 = A sin ωt and e2 = B sin (ωt - Ө) then
A.
C.
e1 lags e2 by Ө
e2 leads e1 by Ө
13. Average value of a sine wave is
A.
True
B. False
B. e2 lags e1 by Ө
D. e1 leads e2 by Ө
2 times the maximum value
C.
Partly true
D. Partly false
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A.C. FUNDAMENTALS
14. Which of the following frequencies has the longest period?
A.
1 Hz
B.
10 Hz
C.
1 kHz
D. 100 kHz
15. RMS value and the mean value is the same in case of
A. square wave
C. triangular scale
B. sine wave
D. half wave rectified sine wave
16. When the sole purpose of an alternating current is to produce heat, the selection of conductor is
based on
A. average value of current
C. rms value of current
B. peak value of current
D. any of the above
17. The form factor of dc supply voltage is always
A.
infinite
B.
zero
C.
0.5
D.
unity
18. The period of the voltage 2 cos 4500πt + 7 sin 7500 πt is
A.
2.51 s
B.
2.51 ns
C. 2.51 ms
D. 2.51µs
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A.C. CIRCUITS (SERIES AND PARALLEL)
1.
The total voltage in a series RL circuit
A. lags, of 90o
C. leads, between 0o and 90o
2.
In a series RL circuit, the inductor current
A. lags
B. leads
3.
The impedance triangle is similar to the
.
A. current, resistor current
C. voltage, impedance
the current by an angle
.
B. lags, between 0o and 90o
D. leads, between 90o and 180o
the resistor current.
C. is equal
D.
is negative
triangle with the resistance phasor in place of the
B. current, resistor voltage
D. voltage, resistor voltage
4.
In the impedance triangle, the inductive reactance and impedance phasor are analogous to the
and
phasor respectively in the voltage triangle.
A. inductive voltage, total voltage
B. inductive current, total current
C. inductive voltage, resistive voltage
D. inductive current, resistive current
5.
In a series RL circuit phasor diagram, total voltage may be presented by the
and the resistor voltage may be represented by the
phasor.
A. current, voltage
B. current resistance, current
C. impedance, resistance
D. impedance, inductance
6.
The phase angle of a series RL circuit is the angle between the
phasor and the
phasor.
A. resistance, inductive reactance
B. resistance, impedance
C. inductive reactance, impedance
D. inductance, impedance
7.
The phase angle of a series RL circuit may be computed
as
or
A. cos–1 R/XL, sin–1 XL/R, tan–1 R/Z
B. cos–1 R/Z, sin–1 XL/R, tan–1 R/XL
C. cos–1 Z/XL, sin–1 R/Z, tan–1 XL/R
D. cos–1 R/Z, sin–1 XL/Z, tan–1 XL/R
8.
A(n)
A.
C.
9.
or _
10. The voltage across a capacitor
lags, 45o
B. lags, 90o
or greater than
D. –1, 0
the current thought it by
C. leads, 0o
.
D. leads, 90o
11. If the resistance in a series RC circuit is increased the magnitude of the phase angle
A. increases
C. decreases
B. remains the same
D. changes in an indeterminate manner
12. In a series RC circuit, the current
A.
C.
.
stores and returns energy to a circuit while a(n)
dissipates energy.
resistor, impedance
B. resistor, inductor
inductor, resistor
D. inductor, reactance
For an RL circuit, the power factor cannot be less than
A. 0, 1
B. 1, 0
C. 0, –1
A.
phasor
lags, of 45o
leads, between 0o and 90o
the total voltage by an angle
B. lags, of 0o
D. leads, of 90o
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.
.
A.C. CIRCUITS (SERIES AND PARALLEL)
13. The resistance phasor for a series RC circuit points out to the right. The capacitive reactance
phasor points
while the diagonal of the rectangle having there two phasors as sides represents
the
.
A. up, impedance
B. down, impedance
C. left, current
D. up, total voltage
14. The phase angle for a series RC circuit is defined as the angle between the
A.
C.
phasors
current, resistance voltage
resistance voltage, capacitor voltage
and the
B. current, total voltage
D. R, XC
15. The phase angle for a series RC circuit may be computed as the angle between the
phasors
A. resistance, impedance
C. resistance, capacitance
and
B. resistance, reactance
D. impedance, reactance
16. The net reactance in a n RLC circuit is
A.
XL
B.
XC
C.
XC – XL
D. XL – XC
17. The impedance of a series RLC circuit is
A.
B.
C.
D.
18. There will
A.
C.
be a frequency, called the
frequency at which
sometimes, natural; XL = XC
B. always, natural; R = 0
always, resonant; XL = XC
D. sometimes, resonant; R = 0
.
19. The formula for the resonant frequency is f =
A.
B.
1
LC
C.
2π
D.
20. For a series RLC circuit at resonance the current amplitude is
amplitude and the power factor is
A. minimum, zero
C. maximum, zero
B. minimum, unity
D. maximum, unity
21. In an RLC circuit, the impedance at resonance is
A.
C.
maximum,
infinity
B. minimum
D. zero
22. The current in RLC series circuit, i.e. at resonance is
A. maximum
C. infinity
B.
D.
minimum
zero
23. In RLC circuits, the current at resonance is
A.
B.
C.
D.
maximum in series circuit and minimum in parallel circuit
maximum in parallel circuit and minimum in series circuit
maximum in both the circuits
minimum in both the circuits
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and for a fixed voltage
A.C. CIRCUITS (SERIES AND PARALLEL)
24. A series resonant circuit is capacitive at f = 100 Hz. The circuit will be inductive somewhere at
A.
B.
C.
D.
f < 100 Hz
f > 100 Hz
f = 100 Hz by increasing the value of the resistance
f=0
25. At a frequency lass than the resonant frequency
A.
B.
C.
D.
series circuit is capacitive and parallel circuit is inductive
series circuit is inductive and parallel circuit is capacitive
both circuits are inductive
both circuits are capacitive
26. In series as well as parallel resonant circuits, increasing the value of resistance would lead to
A.
B.
C.
D.
increase in the bandwidth of both the circuits
decrease in the bandwidth of both the circuits
increase in bandwidth in series circuit and decrease in parallel circuit
decrease in bandwidth in series circuit and increase in parallel circuit
27. The value of current at resonance in a series RLC circuit is affected by the value of
A.
R
B.
C
C.
L
D. all of these
28. In resonant circuits, the power factor at resonance is
A.
zero
B. 1
C. 0.5
D. 0.707
29. Which of the following statements is true for a series RLC circuit tuned at resonant frequency?
A.
B.
C.
D.
the voltage across C > applied voltage
the voltage across L > applied voltage
the voltage across L and C > the applied voltage
the voltage across both L and C < the applied voltage
30. The frequency at which maximum voltage occurs across the inductance in RLC series circuit is
A.
1
B.
1
C.
D.
1
–
2
31. The frequency at which maximum voltage occurs across the capacitance in RLC series circuit is
A.
1
–
B.
C.
1
LC
2
D.
1
1
2L2
2
R
–
2
2L
32. If f1 and f2 are half power frequencies and f 0 be resonance frequency, the selectivity of RLC series
circuit is given by
A.
f2 −
f0
f1 − f0
B.
f2 −
f1
f0
C.
–
–
D.
f2 − f1
2f0
33. In a series RC circuit, the voltage across the capacitor and the resistor are 60 V and 80 V
respectively. The input voltage should be
–37o V
A. 70∠45o V
B. 100
C.
105∠–42o V
D.
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108∠–60o V
A.C. CIRCUITS (SERIES AND PARALLEL)
34. To a series RLC circuit, a voltage of 10 V is applied. If Q of the coil at resonant frequency is 20,
the voltage across the inductor at resonant frequency will be
A. 200 V
B. 100 V
C. 75 V
D. 50 V
35. The currents flowing in L and C at parallel resonance are
A. zero
B. equal
C.
infinite
D.
different
36. The exact natural frequency of free oscillations in an oscillatory circuit with capacitance of 0.055
µF, inductance 2µH and resistance 1 ohm will be
A. 478 kHz
B. 337 kHz
C.
272 kHz
D. 192 kHz
37. A coil with large distributed capacitance has a
A.
C.
low resistance
low resonant frequency
38. The transient currents are due
to
voltage applied to circuit
B. impedance of the circuit
B. low Q
D. high resonant frequency
B.
resistance of the circuit
A.
D. changes in stored energy in inductance
and capacitance
39. To a highly inductive circuit, a small capacitance is added in series. The angle between voltage
and current will
A. increase
C. remain nearly the same
B. decrease
D. become indeterminate
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3-PHASE SYSTEM
1.
In a balanced three phase star connected circuit the line voltages are equal
A. to the line current
B. to the phase voltage
C. and so are the line currents
D. but the line currents are unequal
2.
The type of a.c. distribution system commonly used to supply both light and power is the
A. open delta system
B. three phase delta system
C. three phase star system with neutral wire
D. three phase star system without neutral wire
3.
The phase displacement between phasors in polyphase system is always
A. 90 degrees
B. 30 degrees
C. 120 degrees
D. 360 degrees divided by the number of phases
4.
In a balanced three phase star connected system the line voltage is
A. the phasor difference of the two phase voltages
B. the phasor sum of the two phase voltages
C. 0.707 times the phase voltage
D. 1.414 times the phase voltage
5.
In a star connected system line current is
A. 0.707 times the phase voltage
B. 1.735 times the phase voltage
C. equal to the phase current
D. 1.414 times the phase voltage
6.
The advantages of star connections over delta connections for some phase voltage is that it gives
A. step down current
B. extra step up voltage
C. extra step up current
D. extra step up power
7.
Power in a three phase star system is equal to
A.
3 × VL × IL × power factor
B.
C.
3 × VL × Iph power factor
D.
×
8.
Power in a three phase delta system with balanced load is equal to
A.
3 × VL × IL × power factor
B.
3 × Vph × Iph × power factor
C.
9.
3 × Vph × IL × power factor
×
×
× power factor
3 × Vph × IL × power factor
In a delta connected system the line current is
A. 1.414 times the phase current
C. equal to the phase current
D.
3 × VL × IL × power factor
B. phasor sum of the two phase currents
D. 1.732 times the phase current
10. Power in star connected system is
A.
C.
equal to that of delta system
3 times that of delta system
B.
D.
2 times that of delta system
3 times that of delta system
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3-PHASE SYSTEM
11. For an unbalanced load which connection is suitable
A.
C.
3 wire open delta
3 wire delta connection
B. 4 wire star connection
D. 3 wire star connection
12. What is the minimum number of wattmeters required for measuring power of a three phase
balanced load?
A. two
B.
four
C. one
D. three
13. The power is to be measured for a balanced delta connected load whose terminals cannot be
opened. How many wattmeters do you need?
A. four
B. one
C. two
D. three
14. What is the minimum number of wattmeters required to measure unbalanced power for a three
phase system?
A. two
B.
four
C.
three
D. one
15. In two wattmeter method, the readings of the wattmeter will be identical when
A.
C.
load in one of the phases is zero
power factor is 0.5
B. power factor is unity
D. neutral is earthed
16. Two wattmeters can be used to measure 3-phase power for a
A. balanced and unbalanced load
C. balanced load only
B. unbalanced load only
D. unity power factor only
17. In two wattmeter method, the reading of one of the wattmeter will be zero when
A. power factor is unity
C. load in one of the phases is zero
B. power factor is 0.5
D. a neutral wire is not provided
18. For a three phase unbalanced load
A.
B.
C.
D.
the power factor of each phase will be in proportional to the load
the power factor of each phase will be the same
the power factor of at least one of the phase must be leading
the power factor of each phase may be different
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POWER FACTOR
1.
2.
In a pure reactive circuit, the power factor is
A. lagging
B. zero
C.
Power factor is defines as the ratio of
A. volt amperes to watts
C. volt amperes reactive to watts
B. watts to volt amperes
D. watts to volt amperes reactive
leading
D. unity
3.
In a series circuit consisting of resistance and reactance, power factor is defined as the ratio of
A. resistance to impedance
B. resistance to reactance
C. reactance to impedance
D. reactance to resistance
4.
For a parallel circuit consisting of resistance and reactance, the value of power factor is the ratio
of
A. impedance to reactance
B. reactance to impedance
C. resistance to impedance
D. impedance to resistance
5.
It is not easy to find the value of impedance for a parallel circuit but power factor can easily be
obtained as a ratio of
A. active current to line current
B. reactive current to line current
C. line current to active current
D. line current to reactive current
6.
The power factor of a.c. circuit containing both a resistor and a conductor
is
A. more than unity
B. leading by 90 degrees
C. between 0 – 1 leading
D. between 0 – 1 lagging
7.
In an a.c. circuit, a low value of reactive volt ampere compared with watts indicates
A. high power factor
B. unity power factor
C. leading power factor
D. low power factor
8.
In a given circuit when power factor is unity the reactive power is
A. a maximum
B. equal to I2R
C. zero
D. a minimum
9.
The capacitor of power factor correction are rated in terms of
A. voltage
B. VA
C. kW
D. kVAR
10. Poor power factor results in all of the following except
A. overloading of transformers
C. reduction in power losses
B. overloading of alternators
D. reduction in load handling capacity of electrical
system
11. Power factor of an inductive circuit can be improved by connecting a capacitor to it in
A. series
C. either series or parallel
B. parallel
D. depends on the value of the capacitor
12. For the same load, if the power factor of load is reduced, it will
A. draw more current
C. same current but less power
B. less current
D. less current but more power
13. The power factor of incandescent bulb is
A. 0.8 lagging
B.
0.8 leading
C. unity
D. zero
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POWER FACTOR
14. Power factor of magnetizing component of a transformer is
A. unity
B.
0.8 leading
C.
always leading
D. zero
15. One of the reasons for improving the power factor is
A. to increase the reactive power
C. to increase the real power
B. to decrease the reactive power
D. none of these
16. Another reason for improving the power factor is
A. to avoid poor voltage regulation
C.
to increase the voltage regulation
B.
to keep voltage regulation
constant
D. to decrease the voltage regulation
17. Power factor improvement may be achieved by the use of
A. synchronous motor
C. long transmission line
B. induction motor
D. short transmission line
18. The advantage of using static capacitor to improve the power factor is because they
A.
B.
C.
D.
are not variable
are almost loss free
provide continuous change of power factor
all of the above
19. Many industrial tariffs penalize consumers whose power factor falls
A. below 0.8
C. between 0.8 to 0.95
B. below unity
D. between 0.95 to unity
19. A factory takes a load of 1000 KW and has a reactive power of 1000 KVA. Its power factor is
A. 0.6
B. unity
C.
0.8
D. 0.7
20. A current of 10 amperes at a power factor of 0.8 lagging is taken from 250 V a.c. supply. The
reactive power of the system is
A. 2000 watts
C. 1500 watts
B. 2000 VA
D. 1500 Var
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NETWORK THEOREMS
1.
2.
3.
4.
Kirchhoff’s voltage law is not valid for a non-linear network.
A. True
B. False
C. Partly true
D. Partly False
Kirchhoff's law is applicable to
A. AC circuits only
C. AC as well as DC circuits
B. passive networks only
D. DC circuits only
An ideal current source has zero
A. voltage on no load
C. internal conductance
B. internal resistance
D. current
A closed path made of several branches of the network is known as
A. loop
B. junction
C. branch
D. division
5.
An ideal voltage source is that which
A. has terminal voltage in proportion to current
B. has zero internal resistance
C. has terminal voltage in proportion to load
D. has terminal voltage in proportion to power
6.
A passive network has
A. no source of emf
B. no source of current
C. neither source of current nor source of emf
D. none of these
7.
Which of the following is an active element of a circuit?
A. ideal current source
B. resistance
C. inductance
D. capacitance
8.
The relationship between voltage and current is same for two opposite directions of current in case
of
A. bilateral network
B. active network
C. unilateral network
D. passive network
9.
Which of the following statement is not correct?
A. voltage source is an active element
B. current source is a passive element
C. resistance is a passive element
D. conductance is a passive element
10. A network is said to be non linear if it does not satisfy
A. homogeneity condition
C. both A and B
B. superposition condition
D. associative condition
11. Which of the following statement is not correct?
A.
B.
C.
D.
Ideal voltage source is one whose internal conductance is zero.
Ideal current source is one whose internal conductance is zero.
Ideal voltage source is one whose internal resistance is zero.
Ideal voltage source is one whose generated voltage is equal to the available terminal
voltage.
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NETWORK THEOREMS
12. Which of the following is not a non-linear element?
A. diode
B.
transistor
C.
heater coil
D. electric arc with unlike
electrodes
13. Which of the following theorems enables a number of voltage (or current) source to be combined
directly into a single voltage (or current) source?
A. compensation theorem
B. reciprocity theorem
C. superposition theorem
D. Millman’s theorem
14. Thevenin’s theorem is applicable to network of
A. ac circuit only
C. ac and dc circuit both
B. dc circuit only
D. none of the above
15. For open circuited condition of Thevenin’s theorem, all sources of emf in the network are replaced
by
A. their internal impedance
C. as a total a big source of emf
B. their internal resistance
D. their internal reactance
16. The current in any branch of a network in case of Thevenin’s theorem is the same as if it were
connected to a generator of
A. different rating
C. low rating
B. emf E1 and internal impedance Z1
D. emf E1 and internal impedance zero
17. In order to find Z in Thevenin’s theorem
A. all independent voltage and current sources are short circuited
B. all independent voltage sources are short circuited and independent current sources are
open circuited
C. all independent current sources are short circuited and independent voltage sources are
open circuited
D. all independent voltage sources are open circuited and independent current sources are
open circuited
18. Regarding Thevenin’s equivalent, which of the following is not correct?
A. The voltage source in the Thevenin equivalent circuit is the open circuit voltage of the
network when load is disconnected.
B. The Thevenin equivalent resistance (impedance) is the resistance (impedance) of the
network when all voltage sources are short circuited.
C. Thevenin equivalent resistance is calculated when all voltage sources are open circuited.
D. Thevenin equivalent is the voltage equivalent of the network.
19. Regarding Norton’s equivalent, which of the following is not correct?
A.
B.
C.
D.
Norton’s equivalent is the voltage equivalent of the network.
Norton’s equivalent is the current equivalent of the network.
Norton’s equivalent resistance is the same as the Thevenin equivalent resistance.
The load is connected in parallel to the Norton equivalent resistance and Norton's
equivalent source.
20. Reciprocity theorem is valid for
A. active network only
C. active and passive network both
B. passive network only
D. none of the above
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NETWORK THEOREMS
21. For reciprocity theorem to be applicable to a network in which
A. generators are present
C. inductor is present
B. capacitor is present
D. generators are not present
22. In compensation theorem a network containing generator can be replaced by
A. its zero internal impedance
C. another generator
B.
D.
its infinite impedance
L.C. circuit
23. The most important feature of superposition theorem application is
A.
B.
C.
D.
that the process is eased very much
to find d.c. level in e network that has both sources
that number of equations needed to be solved is reduced very much
none of the above
24. Open circuit voltage is the potential difference between two points when the impedance between
these points is
A. infinity
B.
reactive
C.
zero
D.
capacitive
25. Norton’s theorem reduces a two terminal network to
A.
B.
C.
D.
a constant voltage source and an impedance in parallel
a constant voltage source and an impedance in series
a constant current source and an impedance in parallel
a constant current source and an impedance in series
26. For the same original network end load, Thevenin’s and Norton’s equivalent circuits are related by
A. Eth = InZth = InZn
C. Zn = Eth/Ith
B. Eth = IthZn = IthZth
D. Zth = En/In
27. If an electrical network having one or more than one voltage source, is transformed into equivalent
electrical network with a single voltage source (which is short circuit current of previous circuit)
with parallel internal resistance of the network with all current source replaced by their internal
resistance. The above illustration is called
A. Thevenin’s theorem
B. Reciprocity theorem
C. Norton’s theorem
D. Superposition theorem
28. The superposition theorem requires as many circuits to be solved as there are
A. meshes
B. nodes
C. sources
D. all of the above
29. For maximum power transfer, according to maximum power transfer theorem, source impedance
A.
B.
C.
D.
must be very much large as compared to the load impedance
must be complex conjugate of load impedance
must be equal to load impedance
must be very small as compared to the load impedance
30. In case of delta connected circuit, when one resistor is open, power will be
A. unaltered
B. reduced by 1/3 C. reduced to 1/9
D. reduced to 1/16
31. A source V has an internal impedance Zin = (R + jX) when it is connected ZL = R – jX the power
transferred is
A. V2/4R2
B. V2/4R
C.
V2/R
D. V2/2R
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NETWORK THEOREMS
32. The superposition theorem is applicable to
A.
B.
C.
D.
linear responses only
linear and non-linear responses only
linear, non-linear and time variant response
non-linear responses only
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TRANSFORMERS
1.
2.
3.
The principle of working of a transformer is
A. static induction
C. mutual induction
B. dynamic induction
D. self induction
Transformer is used to change the values of
A. frequency
B. voltage
C.
power
The path of the magnetic flux in a transformer has
A. low reactance B.
high reactance
C. high conductivity
D. power factor
D.
low resistance
4.
Electric power is transformed from one coil to the other coil in a transformer
A. physically
B. magnetically
C. electrically
D. electromagnetically
5.
A transformer operates
A. always at unity power factor
B. has its own power factor
C. at power factor below a particular value
D. at power factor depending on the power factor of the load
6.
The laminations are made from
A. low carbon steel
C. nickel alloy steel stampings
B. silicon steel sheet
D. chrome steel sheets
7.
The steel for construction of transformer core is made so as to have
A. low permeability and high hysteresis
B. low permeability and low hysteresis
C. high permeability and low hysteresis
D. high permeability and high hysteresis loss
8.
The special silicon steel is used for laminations because
A. hysteresis losses are reduced
B. eddy current losses are reduced
C. both the above losses are reduced
D. none of these
9.
What is common in the two windings of a transformer?
A. electric circuit B. magnetic circuit
C. winding wire gauge D.
dielectric circuit
10. The main function of the iron core in a transformer is to
A.
B.
C.
D.
provide strength to the windings
to decrease the hysteresis loss
decrease the reluctance of the magnetic path
reduce eddy current losses
11. Preferably, the resistance between the primary and the secondary of a transformer should be
A.
B.
C.
D.
as low as possible
as high as possible
low or high depending upon whether it is step up or step down respectively
high or low depending upon whether it is step up or step down respectively
12. Ideal transformer assumptions do not include
A. zero reactance of windings
C. no leakage flux
B. zero resistance of windings
D. no saturation of core
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TRANSFORMERS
13. The reactance of a transformer is determined by its
A. leakage flux
C. size of the core
B. common core flux
D. permeability of the material of the core
14. The efficiency of a transformer is normally in the range of
A.
50% to 70%
B.
60% to 75%
C.
80% to 90%
D. 90% to 98%
15. The resistance of low voltage side of a transformer
A.
B.
C.
D.
is equal to resistance of its high voltage side
is more than the resistance of its high voltage side
is less than the resistance of its high voltage side
B or C
16. Eddy current losses in transformer core are reduced by
A.
B.
C.
D.
increasing the thickness of laminations
decreasing the thickness of laminations
taking the wire of higher gauge for winding the transformer
decreasing the air gap in the magnetic circuit
17. The primary and the secondary voltages are
A.
B.
C.
D.
180 degrees out of phase in a transformer
always in phase in a transformer
90 degrees out of phase in a transformer
30 degrees or 60 degrees our of phase in a transformer
18. The basic property of the transformer is that it changes the voltage level of an a.c. signal
A.
B.
C.
D.
without changing the power
without changing its shape
without changing its frequency
without changing power, frequency or shape
19. Eddy current losses in a transformer are minimized by laminating the core, the lamination being
insulated from each other by
A. a light coat of core plate varnish
C. thick paper of insulation
B. thin sheet of mica
D. any one of the above
20. The induced emf in the transformer secondary will depend upon
A.
B.
C.
D.
maximum flux in core and frequencies only
frequency, flux and number of turns in the secondary
frequency of the supply only
number of turns in secondary only
21. At every instant, the direction of secondary current in a transformer must be such as to oppose any
change in flux. This is in accordance with
A. Faraday’s law B. Joule’s law
C.
Lenz’s law
D. Coulomb’s law
C.
E2/E1
D. N2/N1
22. The voltage transformer ratio is
A.
E1/E2
B.
N1/N2
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TRANSFORMERS
23. The magnitude of mutual flux in a transformer is
A.
B.
C.
D.
low at low loads and high at high loads
high at low loads and low at high loads
same at all levels
varies at low loads and constant at high loads
24. The concentric windings are used in core type transformer with
A. LT winding placed next to core
C. LT winding on the outer side
B. HT winding placed next to core
D. HT winding on the outer side
25. Cross-over windings are used for
A.
B.
C.
D.
high voltage winding of small rating transformers
low voltage winding of small rating transformers
high voltage winding of large rating transformers
low voltage winding of large rating transformers
26. In an ideal transformer on no-load, the primary applied voltage is balanced by
A.
C.
the secondary voltage
the secondary induced emf
B. the drop across resistance and reactances
D. the primary induced emf
27. Transformers are rated in
A.
kW
B.
kV
C.
kWH
D. kVA
28. What type of core is used for a high frequency transformer?
A.
air core
B. closed iron core
C. aluminum core
D.
open iron core
29. If in a transformer the secondary turns are doubled and as the same time the primary voltage is
reduced by half, then the secondary voltage will
A. be halved
B. not change
C. be four times as high
D. be reduced to a quarter
30. The no-load current of a transformer in terms of full load current is usually
A.
1 to 3%
B.
3 to 9%
C. 9 to 12%
D. 12 to 20%
31. Which is the common method of cooling a power transformer?
A.
air cooling
B.
air-blast cooling
C.
oil cooling
D. natural cooling
32. Which of the following is a correct statement about eddy currents?
A.
B.
C.
D.
Eddy currents improve the efficiency of a motor.
Eddy currents heat up the metal parts.
Eddy currents do not influence the movement.
Eddy currents are used for arc welding.
33. Which of the statement given below is true about autotransformer?
A. It has two separate windings connected in series externally.
B. It can only step down the voltage.
C. It has only one winding.
D. It is most suitable for power transformation.
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TRANSFORMERS
34. The use of higher flux density in transformer design
A. decreases the weight per kVA
C. increases the weight per kW
B. increases the weight per kVA
D. decreases the weight per kW
35. What is the efficiency of transformer compared with that of electrical motors of the same power?
A.
much smaller
B.
somewhat smaller
C.
much higher
D. about the same
36. The transformer oil used in transformers provide
A.
C.
cooling and lubrication
insulation and cooling
B. insulation and lubrication
D. insulation, cooling and lubrication
37. What is the typical use of an autotransformer?
A.
C.
Toy transformer
Variable Transformer
B. Control transformer
D. Isolating Transformer
38. In any transformer the voltage per turn in primary and secondary remains
A.
C.
always different
always in ratio of k
B. always same
D. sometimes same
39. The full load copper loss in a transformer is 400 watts. At half load, the copper loss will be
A.
400 watts
B. 100 watts
C. 200 watts
D. 50 watts
40. A transformer is working at its maximum efficiency. Its iron loss is 500 watts. Its copper loss will be
A.
300 watts
B.
250 watts
C. 350 watts
D. 500 watts
41. Power transformers are designed to have maximum efficiency at
A.
no load
load
B.
half load
C. near full load
D. little more than full
42. As compared to an amplifier a transformer cannot
A. increase output power
C. increase the output voltage
B. increase the output current
D. decrease the output current
43. Distribution transformers have good all-day efficiency due to
A.
C.
low copper loss
low copper as well as iron loss
B. low iron loss
D. low power loss
44. In transformer the purpose of breather is to
A. extract moisture of the air
C. to provide cooling to the winding
B. to take insulating oil from conservator
D. to provide insulation to the winding
45. Two transformers when operating in parallel will share the load depending upon their
A.
C.
magnetizing current
per unit impedance
B. leakage reactance
D. efficiency
46. The magnetic coupling between the primary and secondary windings of a transformer may be
increased by
A. increasing the number of laminations of core material
B. using the magnetic core of low reactance
C. changing the turns ratio of the transformer
D. no means, because it is constant
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TRANSFORMERS
47. Conservator consists of
A.
B.
C.
D.
an air-tight metal drum fixed at the top of the tank
drum placed at the bottom of the tank
overload protection
none of these
48. For a three phase transformer, turns ratio k is given as
A.
k=
3 × line voltage ratio
B.
C.
k=
3 × phase voltage ratio
D.
k = line voltage ratio
k = phase voltage ratio
49. In a power transformer, the winding which is nearer to the iron core of the transformer
A.
C.
is a H.V. winding
may be H.V. or L.V. winding
B. is L.V. winding
D. is sandwiching of the two windings
50. All day efficiency of a transformer ηA
A.
B.
C.
D.
ηA = electrical efficiency of transformer
ηA > electrical efficiency of transformer
A < electrical efficiency of transformer
none these may be true
51. If we increase the flux density in the case of a transformer
A.
B.
C.
D.
the size of the transformer will reduce
the distortion in the wave shape will reduce
the hysteresis and eddy current losses will reduce
none of the above is true
52. A good transformer oil should be absolutely free from
A.
sulphur
B.
alkalies
C.
moisture
D. all of the above
53. In an ideal transformer on no load, the voltage applied across the primary winding of the
transformer is balanced by
A. the emf induced in the primary winding
B. the drop across the impedance of primary side
C. the drop across the impedance of secondary side
D. the secondary induced emf
54. No load primary input is practically equal to the iron losses in the transformer because
A.
C.
primary current is small
both the currents are small
B. secondary current is small
D. no load is not equal to iron losses
55. The transformation of energy from primary of the transformer to secondary takes place due to
A.
B.
C.
D.
the flux linkage between the two windings
the difference in number of turns of primary and secondary windings
the changing current in two windings
none of these
56. If Rs is the resistance of secondary winding of the transformer and k is transformation ratio then
the equivalent secondary resistance referred to primary side will be
Rs
C. R s
k
k3
A.
B.
D.
Rs
k
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TRANSFORMERS
57. Mark the correct statement.
A.
B.
C.
D.
The percentages of resistance, reactance and impedance have the same value whether
referred to primary or secondary of the transformer.
A good transformer must have regulation as high as possible.
If the power factor is leading the regulation of a good transformer will be higher than when
it is lagging.
None of the above is correct.
58. If the supply frequency to the transformer is increase, the iron loss will
A.
decrease
B. increase
C.
do not change
D. vary
59. The size of a transformer core will depend on
A.
C.
frequency
area of the core
B. flux density of the core material
D. A and B both
60. Two transformers operating in parallel will share the load depending upon their
A.
rating
B.
leakage reactance C. efficiency
D. per unit impedance
61. Three 10 : 1 single phase, step-down transformers are connected in wye-delta. For a primary lineto- line voltage of 3980 V, find the corresponding line voltage on the secondary side.
A. 398 V
B. 230 V
C. 3980 V
D. 2300 V
62. While conducting short-circuit test on a transformer, the following side is short-circuited:
A.
H.V. side
B. L.V. side
C.
Primary side
D. Secondary side
63. Current transformer secondary is connected to an ammeter of 5 A range to measure line current of
1000 A. The ammeter is to be serviced. It can be removed
A. without interfering with supply
B. with interfering with supply
C. only after switching off the main current path
D. only before switching off the main current path
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ALTERNATORS
1.
2.
In huge alternators, the moving part is
A. brushes
B. armature
C. poles
In case of alternator, the stator frame serves
A. to protect the whole machine
C. to hold the armature stampings
B. as a return path for the flux
D. to verticate the armature
D. rotor
3.
Alternators mostly work on rotating field type principle which is different from d.c. machines
where the field is stationary. Therefore alternators
A. don’t obey Faraday’s law
B. work on Faraday’s law
C. do not obey Lenz’s law
D. don’t obey Ohm’s law
4.
High speed alternators have a rotor construction
A. similar to dc machines
B. of non-salient type
C. of salient type
D. of silent type
5.
The voltage applied to the field of a rotating cylindrical rotor type alternators
A. high dc voltage
B. high ac voltage
C. low dc voltage
D. low ac voltage
6.
Alternators are usually designed to generate
A. variable frequency
C. definite frequencies
B. definite currents
D. definite power factor
7.
The standard practice, nowadays in alternators is to have
A. rotating field
B. rotating armature
C. either rotating field or rotating armature
D. none of the above
8.
In power generating stations (thermal stations) the usual number of poles employed in alternators
are
A. twenty four
B. forty eight
C. thirty two
D. none of these
9.
The diameter of high speed turbo alternators as compared to hydroelectric ones are
A. smaller because speed is high
B. smaller because speed is less
C. larger because speed is high
D. larger because speed is less
10. The slip rings employed in a three-phase alternator in hydrostation are insulated for
A.
C.
extra high tension voltage
full armature voltage
B. low voltage
D. very high voltage
11. When the speed of an alternator increases, the frequency
A.
decreases
B.
remains the same
C. increases
D. changes
12. Steam-turbo alternators are much smaller in size than water-turbine alternators for a given
output. This is so because
A. steam-turbo alternators are built with smaller capacities
B. steam-turbo alternators run at high speed
C. steam-turbo alternators have long rotors
D. all of these
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ALTERNATORS
13. For a coil having a span of 2/3 or pole pitch, the coil span factor is
A.
0.8
B. 0.866
C.
0.786
D.
0.966
14. Distributing the armature winding of alternator is more than one number of slots per pole per
phase results in
A. reduction of irregularities produced in the waveform
B. economy of materials used in winding
C. less weight of the entire armature
D. increase of generated emf per phase
15. When the power factor of load is unity, the armature flux of an alternator will be
A.
C.
demagnetizing
cross magnetizing
B. square wave form
D. none of these
16. An alternator is capable of delivering power at a particular frequency. The frequency can be
increased by
A. increasing the armature speed
B. reversing the armature rotation
C. increasing the current supplied to the field electromagnets
D. reversing the field polarity
17. If the input of the prime mover of an alternator is kept constant but excitation is increased then
A.
C.
kVA will be leading
kW will be changed
B. kVA will be lagging
D. the power factor of the load
remains constant
18. For two alternators operating in parallel, if the load shared by one of them i s to be increased, its
field excitation is
A. to be strengthened keeping input torque the same
B. to be weakened keeping input torque the same
C. to be kept constant but input torque should be increased
D. to be kept constant but input torque should be decreased
19. If P = number of pair poles, f = the frequency in Hz, S = speed in rpm, the relationship between the
three for synchronous alternators is given as
P = fS
A. f = PS Hz
120 poles
60
B
.
C.
=
Hz
D.
S = fP
120 rpm
20. If Ө is the angle measured in electrical degrees between any point on the pole face and center of
the pole then for setting a sinusoidal wave as output, the air gap at that point should be such that
A. air gap sin
B. air gap cos θ
α
α
θ
C.
air gap
α
1
D. air gap α
sin θ
21. The sinusoidal voltage developed per pole per phase in a group of coils is defined as
A. Egap = 4.44 NnfkdkpV
C. Egap = 4.44ΦNkffV
B. Egap = 4.44ΦNfkdkpV
D. none of these
Where N = no. of turns per coil
n = no. of coils per phase per pole
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ALTERNATORS
22. The armature reaction of an alternator will be cross-magnetizing of the power factor of the load is
A.
unity
B.
less than unity
C.
more than unity
D.
zero leading
23. If XS = the synchronous reactance of the machine, Xe = leakage reactance and Xa = reactance due
to armature flux then
A. Xa = XS – Xe
B.
Xa = XS + Xe
C.
Xa = Xe – XS
D. Xe = XaXS
24. The best and the most accurate method for determining the voltage regulation is
A.
C.
synchronous impedance method
emf method
B. mmf method
D. Potier triangle method
25. An alternator is said to be over-excited if it is operating at
A.
leading p.f.
B.
lagging p.f.
C.
unity p.f.
D. zero voltage regulation
26. From what source does a rotating field type alternator receive its exciter voltage?
A.
B.
C.
D.
from an externally controlled ac voltage
from an externally controlled dc voltage
from a self excited source like shunt generator
from an auxiliary generator driven by main generator shaft
27. High voltage alternators are usually of the rotating field type. This means the generated voltage is
connected
A. through slip rings to the load
C. directly to the load
B. through slip rings of the rotating field
D. directly to the rotor
28. The maximum current that can be supplied by alternators depends upon the
A. strength of the excite voltage
C. strength of the magnetic field
B. number of poles
D. maximum heat dissipation
29. One of the advantages of distributing the winding in alternators is to
A.
C.
reduce harmonics
reduce the amount of copper
B. improve voltage wave form
D. decrease the value of the voltage
30. Distribution factor K4 is defined as the ration of emf’s of
A.
B.
C.
D.
distributed winding to full pitch winding
concentrated winding to distributed winding
distributed winding to concentrated winding
full pitch winding to distributed winding
31. If n = number of slots per pole per phase and α = slot angle, the distribution factor is
A.
C.
n sin α /
2
B.
sin α / 2
sinn2
sinnα / 2
n sin α / 2
D.
n sin α / 2
32. For a uniformly distributed winding the value of distribution factor is
A.
unity
B.
0.96
C.
0.866
D. 0.955
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ALTERNATORS
33. One of the advantages of a short pitch winding lies in
A.
B.
C.
D.
elimination or suppression of harmonics
reduction of voltage
increasing the inductance
reduction of the circulating current
34. Pitch factor is defined as the ratio of the emf’s of
A.
B.
C.
D.
distributed winding to full pitch winding
short pitch coil to full pitch coil
full pitch winding to short pitch winding
full pitch winding to concentrated winding
35. A winding is short pitched by 60 degrees electrical. Its pitch factor is
A.
0.5
B. 0.866
C.
0.707
D.
0.966
36. Synchronous impedance of an alternator is defined as the ratio of
A.
B.
C.
D.
short circuit voltage to short circuit current
open circuit voltage to short circuit current
short circuit current to no load current
open circuit voltage to short circuit current for same value of excitation
37. Synchronous reactance consists of two components, namely
A.
B.
C.
D.
armature resistance and leakage reactance
leakage reactance and fictitious reactance
armature resistance and fictitious reactance
leakage reactance and capacitive reactance
38. The imaginary or fictitious part of synchronous reactance takes care
A. copper losses
C. armature reaction
of
B. voltage regulation
D. inductive reactance
39. Regulation of an alternator is defined as the rise in terminal
expressed as percentage of the terminal
A. current
B. voltage
when full load is thrown off
for the same value of excitation and speed.
C. rating
D. power factor
40. Synchronization of alternators means
A.
connecting alternators in series
another
C. connecting alternators in parallel
B.
transferring load from one alternator to
D. adjusting the excitation of the alternators
41. To synchronize alternator, three conditions must be fulfilled, namely
A.
B.
C.
D.
same voltage ratio, same frequency and voltages should be in phase with respect to the
external circuit
same voltage, same frequency and voltages should be in phase opposition with respect to
the external circuit
same voltage, same frequency and voltages should be in phase opposition with respect to
local series circuit
same voltage ratio, different frequencies and proper phase relation of the voltages
42. For synchronizing three phase alternators, the additional requirement is that the phase rotation
A. must be the same
C. is anti-clockwise
B. is clockwise
D. none of the above
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ALTERNATORS
43. The method most commonly used for synchronizing the alternators in a power house is:
A.
B.
C.
D.
dark lamp method and a synchroscope
dark lamp method only
bright lamp method
bright lamp method and a synchroscope
44. In order to transfer the load from one alternator to another alternator, when they are operating in
parallel
A. field current is increased
C. speed is decreased
B. field current is decreased
D. prime mover power input is increased
45. Adjustment of field excitation on one of the two alternators operating in parallel will
A.
C.
increase its load
decrease its load
B. change its frequency
D. change its power factor
46. Each of two alternators operating in parallel are adjusted for unity power factor. Increasing the
field current of one
A. causes its power factor to become leading
B. causes its power factor to become lagging
C. changes its speed
D. increases its load
47. What kind of rotor is most suitable for turbo-alternators which are designed to run at high speed?
A. salient-pole type
C. both A and B
B. non-salient pole type
D. none of the above
48. Dampers in large generators
A. increase stability
C. reduce frequency fluctuations
B. reduce voltage fluctuations
D. decrease stability
49. Short-pitch coils in the alternator are used
A. to reduce the size of the alternator
B. to reduce the harmonics from the generated emf of the alternator
C. to reduce the copper loss in the alternator
D. to reduce the core loss in the alternator
50. If the input to the prime-mover of an alternator is kept constant but the excitation is changed then
A.
B.
C.
D.
the reactive component of the output is changed
the active component of the output is changed
the p.f. of the load remains constant
the p.f. of the load varies
51. The driving power from the prime mover driving an alternator is lost but the alternator remains
connected to the supply network and field supply is on. The alternator will
A. get burnt
B. behaves as an induction motor
C. behaves as synchronous motor but will rotate in reverse direction to that corresponding to
generator action
D. behaves as a synchronous motor and will rotate in the same direction
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SYNCHRONOUS MOTORS
1.
2.
Synchronous motor has
A. constant speed
C. high speed at low torque
B. slight drop in speed on full load
D. low speed at high torque
The synchronous speed of a 50 cycle 10 pole motor is
A. 500 rpm
B. 150 rpm
C. 600 rpm
D. 1000 rpm
3.
The speed of a synchronous motor connected to 50 cycle supply is 1000 rpm. The number of poles it
must have
A. 4
B. 6
C. 8
D. 10
4.
The maximum power developed in a synchronous motor occurs at a coupling angle of
A. 0 degree
B. 45 degrees
C. 90 degrees
D. 180 degrees
5.
A 3-phase, 4 pole, 24 slot alternator has its armature coils short-pitched by one slot. Its pitch
factor will be
A. 1.0
B. 0.966
C. 0.96
D. 0.94
6.
Synchronous motor is capable of being operated at
A. lagging power factor only
B. leading power factor only
C. lagging and leading power factor
D. none of these
7.
The synchronous motor is not inherently self-starting because
A. the rotating magnetic field does not have enough poles
B. the rotating magnetic field is produced by only 50 Hz frequency currents
C. the force required to accelerate the rotor is to the synchronous speed in an instant is
absent
D. the starting devices to accelerate the rotor to near synchronous speed is absent
8.
When the stator windings are connected in such a fashion that the number of poles are made half,
the speed of the rotor of a synchronous motor
A. decreases to half the original value
B. remains the same as the original value
C. increases to two times the original value
D. tends to become zero
9.
In a synchronous motor, as load is applied, the motor takes more armature current because
A. back emf decreases causing an increase in motor current
B. the rotor strengthens the rotating field causing more motor current
C. the rotor by shifting its phase backward causes motor to take more current
D. the increased load has to take more current
10. Synchronizing power of a synchronous machine is
A.
B.
C.
D.
equal to synchronous reactance
inversely proportional to the synchronous reactance
directly proportional to the synchronous reactance
none of these
11. Synchronous motor always runs at
A. a speed less than synchronous speed
C. the synchronous speed
B. a speed more than synchronous speed
D. none of these
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SYNCHRONOUS MOTORS
12. Synchronous motors are
A.
C.
self-starting
essentially self-starting
B. not self-starting
D. none of these
13. An over-excited synchronous motor take
A.
C.
lagging current
lagging and leading current
B. leading current
D. none of these
14. The motor in which stator and rotor magnetic field rotate at the same speed is
A.
C.
induction motor
universal motor
B. reduction motor
D. synchronous motor
15. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected,
then
A. the motor stops
C. it runs at lower speed
B.
D.
it runs at the same speed
it runs at very high speed
16. In a synchronous motor, the torque angle is
A.
B.
C.
D.
the angle between the rotating stator flux and rotor poles
the angle between the magnetizing current and back emf
the angle between the supply voltage and the back emf
none of the above
17. A 3-phase, 400 V, 50 Hz, 4-pole synchronous motor has a load angle of 10 degrees electrical. The
equivalent mechanical degree will be
A.
10 degrees
B.
5 2 degrees
C.
5 degrees
D. 1 degree
18. The breakdown torque of a synchronous motor varies as
A.
C.
1
applied voltage
B.
applied voltage
D.
1
(applied voltage)2
(applied voltage)2
19. In a synchronous motor, which loss does not vary with load?
A.
C.
copper losses
windage losses
B. hysteresis losses
D. none of the above
20. A 3-phase, 400 V, 50 Hz salient pole synchronous motor is running on no load. If there is break in
the excitation winding of the motor
A. the motor will stop
B. the winding will get overheated
C. the motor will run as reluctance motor at the rated rpm
D. the motor will run as reluctance motor at lower rpm
21. A 3-phase synchronous motor is running clockwise. In case the direction of its field current is
reversed
A. the motor will continue to run in the same direction
B. the motor will run in the reverse direction
C. the motor will stop
D. the winding of the motor will burn
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SYNCHRONOUS MOTORS
22. The speed regulation of a 3-phase synchronous motor is
A.
5%
B.
1%
C.
0.4%
D. zero
23. In a synchronous motor, the synchronizing power comes into action when
A.
B.
C.
D.
rotor speed is equal to synchronous speed
rotor speed is less than synchronous speed
rotor is speed is more than synchronous speed
rotor speed is either less or more than synchronous speed
24. The speed of a synchronous motor
A.
B.
C.
D.
reduces as load increases
increases as load increases
adjusts itself to new equilibrium speed whenever load changes
always remains constant
25. The minimum armature current of a synchronous motor corresponds to operation at
A. 0.8 power factor lagging
C. zero power factor leading
B. unity power factor
D. zero power factor lagging
26. If the field of a synchronous motor is under-excited the power factor will be
A. lagging
C. unity
B. leading
D. more than unity
27. When a 3-phase synchronous generator is supplying a zero p.f. lagging load the armature field
affects the main field in the following way:
A. directly opposes it
C. augments it directly
B.
D.
cross magnetizes it
indirectly augments it
28. When the excitation of an unloaded salient-pole synchronous motor suddenly gets disconnected
A.
B.
C.
D.
the motor stops
it runs as a reluctance motor at the same speed
it runs as a reluctance motor at a lower speed
none of the above
29. In a 3-phase synchronous converter, the ratio of ac current to dc current is equal to
A.
0.943
B.
0.612
C.
1.60
D. 0.866
30. The armature current of the synchronous motor has large values of
A.
C.
low excitation only
both low and high excitation
B.
D.
high excitation only
moderate excitation
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INDUCTION MOTORS
1.
The type of the motor that does not have a commutator is the
A. repulsion motor
B. induction motor
C. dc shunt motor
D. ac series motor
2.
A certain motor is driven by a 1750 rpm dc shunt motor. If the power supply is to be changed to
three phase, 50 cycles ac, the most suitable replacement motor would be
A. synchronous motor
B. capacitor motor
C. ac commutator motor
D. squirrel cage induction motor
3.
The principle of operation of the induction motor is based on
A. Faraday’s law
B. rotating magnetic field
C. Flemming’s right hand rule
D. Ohm’s law
4.
The rotor of an induction motor gets its power from
A. the line voltage
B. slip rings
C. a centrifugal switch
D. magnetic induction
5.
The induction motors are designed for
A. three phase
C. single phase
B. two phase
D. all of the above
6.
The rotor speed of an induction motor is
A. the same as the synchronous speed
B. faster than the synchronous speed
C. slower than the synchronous speed
D. determined by frequency and the number of poles
7.
The induction motor differs from the synchronous motor in that it(s)
A. requires a dc source for its rotor
B. does not require a rotating magnetic field
C. current is induced in its rotor
D. current I conducted in rotor
8.
To reverse the direction of rotation of a three phase induction motor, it necessary to
A. interchange all the three line connections
B. reverse the polarity of the rotor circuit
C. increase the resistance of the rotor circuit
D. interchange any two of the three line connections
9.
Squirrel cage induction motor differs from the slip ring type in that it has no
A. slip rings
B. rotor winding
C. windings on the stator
D. rotating part
10. If the no-load speed of a squirrel cage induction motor connected to a three phase 50 cycle supply
is 740 rpm. The motor has
A. 2 poles
B. 4 poles
C.
6 poles
D. 8 poles
11. Squirrel cage induction motor has
A.
B.
zero starting torque
very high starting current
B. very small starting torque
D. extra starting torque and it starts up from rest
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INDUCTION MOTORS
12. Just like a dc shunt motor the speed of induction motor operating in stable region
A. decreases with increase in load
C. decreases with decrease in load
B. increases with increase in load
D. none of the above is true
13. Magnetic flux produced due to the stator winding with three-phase current of frequency f and which
is the constant value, rotates at synchronous speed. If P is the number of poles of the motor then
the synchronous speed is given by
120P
A. Ns =
B.
f
C.
Ns = 120fP
D.
60f
Ns = P
14. In an induction motor
A.
B.
C.
D.
rotor runs at a speed equal to the speed of the stator field
rotor runs at a speed which is always lesser than the speed of the stator field
rotor runs at a speed which is always higher than the speed of the stator field
B and C both are correct
15. The difference between the synchronous speed Ns and the actual speed N of the rotor is known as
slip. It can be expressed as a percentage and is given by
—
B. % slip S =
A. % slip S =
×
C.
% slip S =
N − Ns × 100
Ns
D.
% slip S =
N − Ns ×
100 N
(Ns — S)
16. The frequency of the rotor current in an induction motor is given by (If f is the supply frequency, f’
is the rotor frequency and S is the slip)
A. f = Sf’
C. f’ = Sf
B. f’ = Sf’
D. S = f f’
17. Frequency of the rotor in an induction motor in terms of Ns, N and P is given by
N
− N = 120P
f'
A.
B.
C.
D. none of the above is correct
s
18. If E2 = rotor emf/phase at
standstill R2 = rotor
resistance/phase
X2 = rotor resistance/phase at standstill
Then starting torque of an induction motor is given by
A.
Ts =
K 1E2R 2
B.
(R 22 + X 22 )1 2
=
C.
T
s
D.
(R 2 2 + X 22 )
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INDUCTION MOTORS
19. In a 3-phase induction motor, the torque
A.
B.
C.
D.
increases with the increase in supply voltage
decreases with the increase in supply voltage
has no relation with the supply voltage
A and B depending upon the situation
20. Improvement in the power factor in an induction motor
A.
B.
C.
D.
decreases torque
increases the torque
increases the current
increases the torque and decreases the current due to increased impedance
21. Torque in an induction motor under running condition is given by
A.
K1E22R 2
T=
C.
K1E22R 2
B.
T=
D.
T = K 1SE2 R 2
2
R 22 + X 22
22. In an induction motor the torque is related with the supply voltage as
A.
T α V1
2
C.
B.
TαV
D.
Tα1
V
2
23. The maximum torque under running condition in terms of rotor reactance is given by
A.
C.
Tma
x
= KφSE2
2X 2
=
B.
= KφE 2
= KφSE2
T
max
2
X2
D.
T
max
2X 22
24. Torque under running condition is maximum at the slip S
A.
B.
C.
D.
which makes rotor reactance/phase equal to rotor resistance/phase
which makes rotor reactance/phase greater than rotor resistance/phase
which makes rotor reactance/phase lesser than rotor resistance/phase
which is independent of rotor resistance
25. The value of slip at maximum torque condition (under running condition) in terms of R2 and X2 is
X
A.
S=
C.
S=
B.
2
2
X2
D.
=
S = E2
2X 2
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INDUCTION MOTORS
26. Short circuit test on the induction motor can be used to find out
A.
B.
C.
D.
the transformation ratio of the induction motor
power scale of circle diagram
copper losses in the induction motor
all of the above
27. Which of the following is a correct relation for an induction motor?
A.
B.
C.
D.
rotor efficiency = actual speed of rotor
synchronous speed
rotor on losses = slip x rotor input
rotor input = 2tt x gross torque x synchronous speed
all of the above relations are correct
28. Two of the power supply terminals to a 3-phase induction motor got interchanged during
reconnection after maintenance of the motor, when put back into service, the motor will
A. fail to rotate
B. rotate in the same direction as it was prior to maintenance
C. rotate in the reverse direction to that prior to maintenance
D. stop
29. A 400 kW, 3-phase, 440 V, 50 Hz induction motor has a speed of 950 rpm on full load. The machine
has 6 poles. The slip of the machine will be
A. 0.06
B. 0.10
C.
0.04
D. 0.05
30. If the air gap of the induction motor is increased
A.
B.
C.
D.
the magnetizing current will decrease
the magnetizing current will increase
the power factor will decrease
none of the above is correct
31. In a slip-ring induction motor resistance is connected in rotor phases
A.
B.
C.
D.
to limit starting current
to increase the starting current
to limit starting current and increase starting torque
none of the above statement is correct
32. For a 3-phase, wound-rotor induction motor, as increase in rotor resistance affects the motor
performance in the following way
A. the starting current decreases
B. the motor efficiency decreases
C. the maximum torque is reduced
D. the starting current decreases
33. It is advisable to avoid line starting of induction motor and use starter because
A.
B.
C.
D.
starting torque is very high
motor takes five to seven times its full load current
it will pick-up very high speed and may go out of step
it will run in reverse direction
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INDUCTION MOTORS
34. A change of 5% in the supply voltage of a 3-phase induction motor will produce to its torque a
change of approximately
A. 5%
B.
25%
C.
10%
D. 20%
35. A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs.
What will eventually happen? It will
A. start after some time
B. continue to run at lower speed without damage
C. get heated and consequently get damaged
D. continue to run then stop after some time
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ELECTRICAL MEASURING INSTRUMENTS
1.
When using any instrument for measurement or testing an electrical circuit, your
considered first
A. personal safety
B. theoretical knowledge
C. surrounding
D. dress
2.
The resolution of an indicating instrument is
A. the smallest change in the output reading due to drifting of pointer
B. the smallest change in applied stimulus that will indicate a detectable change in deflection
C. the difference between various readings for the same applied stimulus
D. the difference between various readings for the difference applied stimulus
3.
What should be the accuracy classes of industrial measuring instruments?
A. Accuracy classes 1.0, 0.2 and 0.5
B. Accuracy classes 0.5, and 1
C. Accuracy classes 0.5, 1.0, 1.5, 2.5 and 5
D. Accuracy classes 1.0, 1.5, 2.5 and 5
4.
What is the purpose of providing a mirror behind the pointer in measuring instruments?
A. The scale is illuminated through the mirror
B. With the help of the mirror it can be seen whether the pointer is bent or not
C. The mirror is semi-transparent so as to allow the observation of the interior of the
instrument
D. Reading errors due to inclined observation are eliminated by removing parallax between
the pointer and its image in the mirror
5.
Which of the following statements about the internal resistance of measuring instruments is true?
A. The internal resistance of ammeters should be very small and that of voltmeters very high
B. The internal resistance of ammeters should be very high and that of voltmeters very small
C. The internal resistance of ammeters and voltmeters should be very small
D. The internal resistance of ammeters and voltmeters should be very high
6.
Meter accuracy is determined by
A. half-scale deflection
C. one-fourth of full-scale deflection
B. full-scale deflection
D. one-tenth of full-scale deflection
7.
The reliability of an instrument means
A. the life of the instrument
B. the extent which the characteristics remain linear
C. degree to which repeatability continues to remain with specific limits
D. all of these
8.
Threshold of sensitivity with respect to instruments
is
A. the maximum signal which can be measured
B. the value of sensitivity on the highest scale
C. the value of sensitivity on the lowest scale
D. the smallest signal that results in a detectable output
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should be
ELECTRICAL MEASURING INSTRUMENTS
9.
Sensitivity inaccuracy of a recording instrument means
A. the amount of input required to produce unit pen deflection
B. the smallest signal required to produce detectable output
C. the maximum error in sensitivity displayed by a pen
D. degree to which the instrument is not sensitive enough to repeat readings
10. On which of the following factors the sensitivity inaccuracy of an instrument does not depend?
A.
C.
hysteresis or dead bond
frequency response
B. amplitude distortion
D. all of these
11. Damping provides
A. braking action on a meter pointer
C. starting torque on the meter pointer
B. good accuracy
D. counter torque to deflection torque
12. In moving-coil meters, damping is provided by
A. the aluminum frame
C. damping vane in an air tight chamber
B. damping vane
D. none of these
13. Moving coil instruments are used
A.
C.
in ac circuits only
in dc circuits only
B. both in ac and dc circuits
D. for measuring voltage only
14. To reduce the effect of a voltmeter upon the circuit under test, we should
A.
B.
C.
D.
decrease the multiplier resistance
get an instrument with a higher internal resistance
use a parallel resistor
use an ac meter with rectifier
15. To increase the range of a voltmeter
A.
B.
C.
D.
a low resistance is connected in series
a low resistance is connected in parallel
a high resistance is connected in series
a high resistance is connected in parallel
16. What is the function of the zero-adjust control in a multimeter?
A.
B.
C.
D.
It serves to conduct the current.
With this control, the sensitivity of the meter can be changed.
The zero point is corrected with the help of this control.
The moving parts can be tightened to the casing with the help of this control-screw
17. If moving-iron type ammeter is connected to a circuit, and we interchange its connection, then
A.
B.
C.
D.
it will give no deflection
its reading will not change
it will deflect in the opposite direction
it will burn out
18. Which of the following damping methods is common in moving coil instruments?
A. air damping
C. spring damping
B. fluid damping
D. eddy-current damping
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ELECTRICAL MEASURING INSTRUMENTS
19. The main reason for using springs in a measuring instrument is
A.
B.
C.
D.
to conduct the current to the coils
to hold the pivot in position
to control the pointer movement
to minimize the vibration of the pointer
20. A moving-iron type instrument has
A.
B.
C.
D.
a linear scale (uniform scale)
a nonlinear scale
its deflection directly proportional to the current
its deflection directly proportional to the voltage
21. In moving-coil instruments, the scale used is
A.
C.
nonlinear scale
square law scale
B. linear scale
D. log scale
22. Two meters X and Y require 40 mA and 50 mA, respectively, to give full scale deflection, then
A.
B.
C.
D.
X is more sensitive
Y is more sensitive
both are sensitive
sensitivity cannot be judged with the given information
23. The function of a shunt in an ammeter is to
A.
B.
C.
D.
bypass the current
increase the current in the coil
decrease the voltage drop
increase the meter resistance
24. The shunt resistance in an ammeter is usually
A.
B.
C.
D.
less than meter resistance
equal to meter resistance
greater than meter resistance
of any value
25. External shunts are generally used for measuring currents greater than about
A.
5A
B.
10 A
C. 15 A
D. 30 A
26. If the approximate value of the current to be measured is not known, measurement should start on
A.
B.
C.
D.
the lowest range and then increase the range
the highest range and then increase the range
the middle range and then decrease the range
the middle range and then increase the range
27. Sensitivity of a voltmeter is expressed as
A.
Volts/Ohm
B. Ohms/Volt
C. Ohms-Volt
D. 1/Ohms Volt
28. A low voltage is measured on a higher scale of a voltmeter. The measurement would have
A.
low accuracy
B.
low resolution
C.
low precision
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D. all of these
ELECTRICAL MEASURING INSTRUMENTS
29. The disadvantage associated with an electrodynamic instrument is that
A.
it consumes more power
C.
its frequency range is low
B.
it has low torque to weight
ratio
D. all of these
30. An electrodynamic meter can be used to measure
A.
C.
ac voltage
dc as well as ac voltage
B. dc voltage
D. dc voltage but for ac voltages rectification is
necessary
31. Megger is an instrument to measure
A.
C.
very low resistance
Q of a coil
B. insulation resistance
D. inductance of a coil
32. Megger essentially is a
A. megohmmeter
C. series-type ohmmeter
B.
D.
shunt-type ohmmeter
dynamometer
B.
D.
moving-iron meter
electrostatic meter
33. Megger in its operation is based upon
A. moving-coil meter
C. dynamic-meter meter
34. Which of the following equipment is not a part of megger?
A.
C.
hand crank
a coil of high inductance
B. moving-coil meter
D. gear box generator
35. The number of coils in the meter of megger is
A.
C.
one
three
B. two
D. four
36. With the measurement terminals open-circuited, the ‘infinity’ reading of megger is due to
A.
B.
C.
D.
current in the coil is connected across the measurement points
unit in the coil connected across the generator
current in both the coils
zero deflection of the pointer
37. A multimeter consists of
A.
B.
C.
D.
voltmeter and ohmmeter
voltmeter and current meter
current meter and ohmmeter
voltmeter, current meter and ohmmeter
38. A VTVM is more reliable as compared to multimeter for measuring the voltage across low
impedance because
A. its sensitivity is very high
B. if offers high input impedance
C. it does not alter the measured voltage
D. all of these
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ELECTRICAL MEASURING INSTRUMENTS
39. The simplest and most convenient form of detector used in a Wheatstone bridge for audio
frequency range is
A. galvanometer
B. vibration galvanometer
C. pair of headphones
D. cathode ray tube indicator
40. Inductance is measured in terms of capacitance and resistance by
A.
C.
Schering bridge
Maxwell-Wein bridge
B. Anderson bridge
D. Wein bridge
41. Carey-Foster bridge is specially designed to determine.
A.
B.
C.
D.
the high resistance of the wire
the internal resistance of the battery
the difference between two nearly equal resistances
the emf of the voltage source
42. Schering bridge can be used to measure
A.
B.
C.
D.
capacitance and its power factor
Q of a coil
inductance and its Q-value
very small resistance
43. Which of the following bridges is used to measure inductance of the high Q-inductor?
A.
B.
C.
D.
Maxwell bridge
Hay bridge
Wein bridge
Anderson bridge
44. Which of the following bridge is used to measure inductance of a low Q-inductor?
A.
C.
Maxwell bridge
Wein bridge
B.
D.
Hay bridge
Anderson bridge
45. The potentiometer wire should have
A.
B.
C.
D.
high specific resistance and high temperature coefficient
high specific resistance and low temperature coefficient
low specific resistance and high temperature coefficient
low specific resistance and low temperature coefficient
46. Sensitivity of a potentiometer can be increased by
A.
B.
C.
D.
decreasing the length of potentiometer wire
increasing the length of potentiometer wire
decreasing the current of potentiometer wire
decreasing the resistance in the rheostat series with the battery
47. The cell is used in a potentiometer is
A.
C.
a Dry cell
a Leclanche cell
B. a Daniel cell
D. a Lead accumulator
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ELECTRICAL MEASURING INSTRUMENTS
48. Induction type single-phase energy meter is
A.
B.
C.
D.
an ampere-hour meter
true watt-hour meter
wattmeter
none of these
49. A wattmeter can measure
A.
C.
ac power only
ac as well as dc power
B. dc power only
D. dc power and ac power after rectification
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CIRCUIT BREAKERS
1.
2.
The function of protective relay in a circuit breaker is
A. to earth any stray voltages
B. to close
the contacts
when
the actuating
quantity
predetermined value
C. to limit arcing current during the operation of circuit breaker
D. to provide additional safety in the operation of circuit breaker
Low voltage circuit breakers have rated voltages of less than
A. 220 V
B. 400 V
C. 1000 V
reaches
a
certain
D. 10,000 V
3.
A relay in which the measurement is performed by a stationary circuit and which has no moving
parts is known as
A. Static relay
B. Differential relay
C. Instantaneous relay
D. Time relay
4.
When a H.V. ac circuit breaker is tested for endurance, it is tested for at least
A. 1000 opening-closing operations
B. 100 opening-closing operations
C. 10 opening-closing operations
D. 5 opening-closing operations
5.
For high voltage ac circuit breakers, the rated short circuit current is pas sed for
A. 0.01 sec
B. 0.1 sec
C. 3 sec
D. 30 sec
6.
Which of the following is not a type of contactor for circuit breakers?
A. electromagnetic
B. electro-pneumatic
C. pneumatic
D. vacuum
7.
Interrupting medium in a contactor may be
A. air
C. SF6 gas
B. oil
D. any of the above
8.
In air blast circuit breakers, the pressure of air is of the order of
A. 100 mg Hg
B. 1 kg/cm2
C. 20 to 30 kg/cm2
D. 200 to 300 kg/cm2
9.
SF6 gas
A. is lighter than hydrogen
B. is lighter than air
C. has density 2 times as compared to that of air
D. has density 5 times as compared to that of air
10. The pressure of SF6 gas in circuit breakers is of the order of
A. 100 mg Hg
C. 3 to 5 kg/cm2
B. 1 kg/cm2
D. 30 to 50 kg/cm2
11. While selecting a gas for circuit breaker, the property of gas that should be considered i s
A. high dielectric strength
C. non-toxicity
B. non-inflammability
D. none of the above
12. Out of the following circuit breakers, which one has the lowest voltage range?
A. air-break circuit breaker
C. Air-blast circuit breaker
B. tank type oil circuit breaker
D. SF6 circuit breaker
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CIRCUIT BREAKERS
13. Which of the following circuit breaker can be installed on 400 kV line
A.
B.
C.
D.
Tank type coil circuit breaker
Miniature circuit breaker
Vacuum circuit breaker
Air blast circuit breaker
14. In a HRC fuse the time between cut-off and final current zero, is known as
A.
B.
C.
D.
total operating time
arcing time
pre-arcing time
any of the above
15. Fusing factor for HRC fuse is
A.
B.
Minimum fusing current
Minimum rupturing time
C.
Maximum fusing current
Minimum rupturing
time
D.
Prospective current of a circuit
16. The insulation resistance of high voltage electric circuit breaker is
A. 1 kΩ
C. 20 Mega ohms
B. 10 kΩ
D. 2000 Mega ohms
17. There is definite objection to use of which of the following medium for extinguishing the arc in case
of a circuit breaker?
A. Air
C. Vacuum
B. SF6 gas
D. Water
18. In a circuit breaker if the insulation resistance between phase terminal earthed frame is less than
the specified limit, the probable cause could be
A. moisture
B. dirty insulation surface
C. carbon or copper particle sticking to the internal surface
D. any of the above
19. The transient voltage that appears across the contacts at the instant of arc extinction is called
A.
B.
C.
D.
recovery voltage
restriking voltage
supply voltage
peak voltage
20. In a circuit breaker the active recovery voltage depends upon
A.
B.
C.
D.
power factor
armature reaction
circuit conditions
all of the above
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CIRCUIT BREAKERS
21. Best protection is provided by HRC fuse in case of
A.
B.
C.
D.
Open circuits
Short circuits
Over loads
None of the above
22. A fuse wire possesses
A. inverse time characteristics
B. direct time characteristics
C. neither of the above
23. A relay used for protection of motors against overload is
A.
B.
C.
D.
impedance relay
Electromagnetic attraction type
Thermal relay
Buchholz’s relay
24. Fuse protection is used for current ratings up to
A. 10 A
B.
20 A
C. 50 A
D. 100 A
25. The fuse current in ampere is related with fuse wire diameter D as
A.
1α1
D
B.
1αD
C.
D.
1 α D2
26. A fuse wire should have
A.
B.
C.
D.
low specific resistance and high melting point
low specific resistance and low melting point
high specific resistance and high melting point
high specific resistance and low melting point
27. Fuse wire protection system is usually used beyond
A. 10 A
B.
25 A
C.
50 A
D. 100 A
28. For extra high voltage lines which circuit breaker is preferred
A.
B.
C.
D.
Bulk oil circuit breaker
Vacuum circuit breaker
SF6 gas circuit breaker
Minimum oil circuit breaker
29. The number of cycles in which a high speed circuit breaker can complete its operation is
A. 3 to 8
B.
10 to 18
C.
20 to 30
D.
40 to 50
30. A material best suited for manufacturing of fuse wire is
A. Aluminum
B. Silver
C.
Lead
D. Copper
31. In a circuit breaker, the current which exists at the instant of contact separation is known as
A. restriking current
C. breaking current
B. surge current
D. recovery current
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CIRCUIT BREAKERS
32. A Merz-Price protection is suitable for
A. transformers
C. feeders
B. alternators
D. transmission lines
33. ‘Kick fuse’ has
A. square law characteristics
C. inverse characteristics
B. linear characteristics
D. direct characteristics
34. Air-blast breakers for 400 kV power systems are designed to operate in
A. 50 microseconds
C. 500 milliseconds
B. 50 milliseconds
D. 50 seconds
35. Breaking capacity of a circuit breaker is usually expressed in terms of
A. amperes
B.
volts
C.
MW
D. MVA
36. Which of the following equations correctly represents the relation between contact resistance r
and the applied force F?
A.
F=
k.r
B.
F=k
r
C.
D.
r = kFn
37. As the force on contact is increased, the contact resistance will
A. increase linearly
C. remain altered
B. increase exponentially
D. decrease
38. The heat produced at the contact point, due to passage of current, will least depend on
B.
C.
contact resistance
current flowing
B. time during which the current flows
D. temperature of the surrounding medium
39. Minimum arcing voltage for platinum is 16 V. It can be therefore concluded that when the voltage is
below 16V
C. it will not possible to interrupt the circuit
D. it will possible to pass the current
E. it will be possible to interrupt any value of current without arcing
F. it will be possible to interrupt any value of current without bringing contact closer to
another
40. Which of the following is not the method of arc dispersion?
G. oil immersion contacts
C. use of rectifiers
B. magnetic blow out of arc
D. deionization of arc path
41. Which of the following contact point metals has the highest melting point?
A. Silver
B.
Tungsten
C. Gold
D. Copper
42. The arc voltage produced in the circuit breaker is always
A. in phase with arc current
C. lagging the arc current by 90o
B. leading the arc current by 90o
D. leading the arc current by 45o
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CIRCUIT BREAKERS
43. Sparking between contacts can be reduced by
H.
I.
J.
K.
inserting resistance line
inserting a capacitor in series with the contacts
inserting a capacitor in parallel with the contacts
inserting an inductor in series with the contacts
44. For magnetic blow out of arc the magnetic field is produced
L.
M.
N.
O.
in the load circuit
parallel to the axis of the arc
at right angle to the axis of the arc
at 45 degrees with respect to the axis of the arc
45. Sparking occurs when a load is switched off because the circuit has
P.
C.
high inductance
high resistance
B. high capacitance
D. low resistance
46. For the same current, which of the following fuse wires will have the least fusing time?
Q. 18 SWG TIN – 12.5 A
C. 22 SWG TIN – 7.5 A
B. 20 SWG TIN – 10 A
D. 24 SWG TIN – 5 A
47. An automatic device that operates at present value is known as
A.
C.
mercury switch
fuse
B. relay
D. contactor
48. The basic function of a circuit breaker is to
A. produce arc
C. transmit voltage by arcing
B. ionize the surrounding air
D. extinguish the arc
49. The power factor of arc in the circuit breaker is
A. always zero
C. always lagging
B. always unity
D. always leading
50. Flame proof switch gears are usually preferred
A. on transmission lines of low voltage
C. in mines
B. substations
D. in high MVA capacity circuits
51. Air is used in air-blast circuit breaker
A. must have least carbon dioxide
C. must be free from moisture
B. must be ionized
D. none of these
52. In a circuit breaker the time duration from the instant of fault to the instant of energizing of the
trip coil is known as
A. lag time
B.
lead time
C. protection time
D. operation time
53. In a circuit breaker the time duration from the instant of the fault to the extinction of arc is known
as
A. operation time
C. lag time
B. total clearing time
D. lead time
54. In a circuit breaker the time duration from the instant of fault to the instant of closing of contact
is known as
A. recycle time
B.
total time
C.
gross time
D. reclosing time
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CIRCUIT BREAKERS
55. For high speed circuit breaker the total clearing time is nearly
A. 1 to 2 cycles
B.
5 to 10 cycles
C.
10 to 15 cycles
D. less than 50 cycles
56. If the power is zero, the active recovery voltage will be
A.
B.
C.
D.
minimum
0.5
0.707
maximum
57. A circuit breaker will normally operate
A.
B.
C.
D.
when the switch is put on
when the line is to be checked
when the power is to be supplied
whenever fault in the line occurs
58. Which of the following circuit breaker will produce the least arc energy?
A.
B.
C.
D.
minimum oil circuit breaker
air blast circuit breaker
plain oil circuit breaker
all will produce the same energy
59. The breaking capacity of a circuit breaker in MVA ( 3 phase ) is given by
A. rated service voltage x rated symmetrical current
B. 1.1 x rated service voltage x rated symmetrical current
C.
2 x rated service voltage x rated symmetrical current
D.
x rated service voltage x rated symmetrical current
60. Which relay is used for feeders?
A. MHO relay
C. Merz-Price protection
B. Translay relay
D. Buchholz relay
61. Which of the following relays is used in transformers?
A.
B.
C.
D.
Buchholz relay
MHO relay
Merz-Price relay
None of the above
62. MHO relay is used for
A.
B.
C.
D.
rectifier
circuit breaker
transmission lines
feeders
63. Merz-Price protection is used on
A.
B.
C.
D.
substations
capacitor banks
induction motors
generators
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CIRCUIT BREAKERS
64. The value of the fault current depend on
A.
B.
C.
D.
voltage at the faulty point
total impedance up to the fault
both A and B
none of the above
65. The advantage of the neutral earthing is
A.
B.
C.
D.
simplified design of earth fault protection
over-voltages due to the lightening can be discharges to the earth
freedom from persistent arcing grounds
all of the above
66. The over voltage surges in power system may be caused by
A.
B.
C.
D.
lightening
switching
resonance
any of the above
67. The protection against the over-voltage due to the lightning is provided by
A.
B.
C.
D.
use of surge diverters
low tower footing resistance
use of overhead ground wires
any of the above
68. Which of the following is a conducting medium for electric current?
A.
B.
C.
D.
Low temperature gas
High temperature gas
Dissociated gas
Plasma
69. In circuit breakers the contact space is ionized by
A.
B.
C.
D.
thermal ionization of gas
thermal emission from surface contacts
field emission from the surface contacts
any of the above
70. Which of the following are air-break switching devices?
A.
B.
C.
D.
Isolator
Limit switch
Earthing switch
All of the above
71. Which of the following is the deremit of SF6 circuit breakers?
A.
B.
C.
D.
Sealing problem of gas
In flux of moisture in the gas system is dangerous
Deterioration of quality of circuit breaker affects reliability of circuit breakers
All of the above
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CIRCUIT BREAKERS
72. A fuse is normally a
A.
B.
C.
D.
current limiting device
voltage limiting device
power limiting device
power factor limiting device
73. Normally the fuse elements are in parts which are connected in the middle by tin bridge. The
melting point of tin bridge is
A. 35oC
B. 88oC
C. 230oC
D. 540oC
74. The material used for bus bars should have
A.
B.
C.
D.
low resistivity
higher softening temperature
low cost
all of the above
75. Which of the following is not valid in case of aluminum as compared to copper? Aluminum is higher
A.
B.
C.
D.
resistivity
coefficient of linear expansion
tensile strength
joint resistance
76. Over current protection for motor is provided by
A. cartridge fuses
C. over current relay
B. kit kat fuses
D. all of the above
77. Fuse in motor circuits provides
A. over current protection
B. short-circuit protection
C. open-circuit protection
D. none of the above
78. In which method of starting a motor, the starting current is the maximum?
A.
B.
C.
D.
Auto-transformer
Star-delta transformer
Stator rotor starter
Direct-on-line
79. Over voltage transients may occur due to
A.
B.
C.
D.
lightening
switching
arcing grounds
any of the above
80. Switching surges may be caused by
A.
B.
C.
D.
closing of the unchanged line
load shedding or receiving end of line
switching of magnetizing current
any of the above
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CIRCUIT BREAKERS
81. The disadvantages offered by underground system is
A.
B.
C.
D.
frequent arcing grounds
difficult earth fault relaying
voltage oscillations
all of the above
82. Solid grounding is used for voltages
A.
B.
C.
D.
above 220 kV
above 11 kV
below 660 V
below 115 V
83. Switching over voltages are more hazardous than lightening surges in case of
A.
B.
C.
D.
low voltage systems
11 kV system
unbalanced systems
EHV and UHV systems
84. Current limiting reactors may be
A.
B.
C.
D.
air cooled, air cored
oil immersed magnetically shielded
oil immersed non-magnetically shielded
any of the above
85. Series reactors are installed at strategic locations of the power systems to
A.
B.
C.
D.
bring down the fault level within the capacity of the switchgear
directly pass the fault surges to ground
pass the neutralizing surges of opposite nature
discharge the capacitor
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GENERATION OF ELECTRIC POWER
1.
Which of the following generating stations has maximum running cost?
A. thermal power station
B. nuclear power
station
C. hydro power station
D. none of these
2.
Which of the following methods of generating electric power from the sea water is more
advantageous?
A. water power
B. ocean power
C. tidal power
D. none of these
3.
Out of the following, which one is not unconventional source of energy?
A. tidal power
B. geothermal power
C. nuclear energy
D. wind energy
4.
Heating value of coal largely depends on
A. ash content
C. volatile matter
B.
D.
moisture content
size of coal particles
5.
Power plants using coal work closely on which of the following cycle?
A. Rankine cycle
B. Binary vapor cycle
C. Otto cycle
D. Brayton cycle
6.
The efficiency of a thermal power plant improves with
A. increased quantity of coal burnt
B. use of high steam pressures
C. lower load in the plant
D. larger quantity of water used
7.
Which of the following contributes to improvement of efficiency of Rankine cycle in a thermal
power plant?
A. use of high pressures
B. regeneration use of steam for heating boiler feed water
C. reheating of steam at intermediate stage
D. all of the above
8.
Which of the following is not a high pressure boiler?
A. Loeffer boiler
B. Lancashire boiler
C. Velox boiler
D. La-Mount boiler
9.
Overall thermal efficiency of a steam power station is in the range
A. 18-24%
B. 30-40%
C. 44-62%
D. 68-79%
10. In a steam turbine cycle, the lowest pressure occurs in
A. turbine outlet
C. condenser
B. boiler
D. superheater
11. Chemical composition of coal is given by
A.
C.
Proximate analysis
Orost analysis
B. Ultimate analysis
D. All of the above
12. For low head and high discharge, the hydraulic turbine used is
A. Kaplan turbine
C. Pelton wheel
B. Francis turbine
D. Jonval turbine
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GENERATION OF ELECTRIC POWER
13. A graphical representation between discharge and time is known as
A. Monograph
C. Hydrograph
B. Hectograph
D. Topograph
14. A Pelton wheel is
A. axial flow impulse turbine
C. outward flow impulse turbine
B. inward flow reaction turbine
D. inward flow impulse turbine
15. A Francis turbine
A. outward flow impulse turbine
C. inward flow impulse turbine
B.
D.
outward flow reaction turbine
inward flow reaction turbine
16. Spouting velocity is
A. 50% of ideal velocity of jet
C. ideal velocity of jet
B. actual velocity of jet
D. velocity of jet under specified condition
17. A Kaplan turbine is
A. a high head mixed flow turbine
C. a reaction turbine, outward flow type
B. an impulse turbine, inward flow type
D. low head axial flow turbine
18. Outward radial flow turbines
A.
B.
C.
D.
are impulses turbines
are reaction turbines
are partly impulse partly reaction turbines
may be impulse or reaction turbines
19. In an impulse turbine
A.
C.
always operates submerged
B. makes use of a draft tube
is most suited for low head installation D. operates by initial complete conversion to
kinetic energy
20. A gas turbine works on
A.
C.
Carnot cycle
Dual cycle
B. Brayton cycle
D. Rankine cycle
21. Maximum efficiency of an open cycle gas turbine is nearly
A.
C.
40%
60%
B.
D.
50%
30%
22. Compressor used in gas turbine is
A.
C.
screw compressor
plunger type compressor
23. Overall efficiency of gas turbine is
A. equal to Carnot cycle efficiency
C. less than Diesel cycle efficiency
B. multistage axial flow compressor
D. reciprocating compressor
B. equal to Rankine cycle efficiency
D. more than Otto or Diesel cycle
efficiency
24. The compressor ratio in case of diesel engine is
A. 5 to 7
B.
7 to 10
C.
14 to 22
D. 25 to 36
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GENERATION OF ELECTRIC POWER
25. High horse power diesel engines are started by
A. self starter
B.
cranking
C.
battery
D. compressed air
C. ethyl alcohol
D. all of the above
26. Which of the following is a non-petroleum fuel?
A. benzol
B.
methyl alcohol
27. Diesel engine fuels are rated by
A. Octane number
C. Cetane number
B. H.U.C.R.
D. CRF number
28. Air standard efficiency of a diesel engine depends on
A. compression ratio
C. fuel
B. speed
D. torque
29. Which engine has the highest air fuel ratio?
A. Petrol engine
C. Diesel engine
B. Gas engine
D. Gas turbine
30. Most of heat generated in internal combustion engine is lost in
A. cooling water
C. lubricating oil
B. exhaust gases
D. radiation
31. The internal combustion engines never work on
A. Diesel cycle
C. Otto cycle
B. Rankine cycle
D. Dual combustion cycle
32. The efficiency of thermal plant is approximately
A. 10%
B. 30%
C.
60%
D. 80%
33. Which of the following is not a secondary nuclear fuel?
A. U-235
B.
U-233
C.
plutonium
D. Pn-239
34. The function of moderator in nuclear reaction is
A. to accelerate the reaction
C. to absorb excessive neutrons
B. to control the reaction
D. to liberate excessive neutrons
35. Heavy water is
A. H2O
B. D20
C.
W2O
D. B2O
36. Nuclear reactors generally employ
A. fusion
C. both fusion and fission
B. fission
D. none of the above
37. In water turbine, the runway speed of Pelton turbine is
A. 1.8 times the rated speed
C. 2.5 to 2.8 times the rated speed
B. 2 to 2.2 times the rated speed
D. 3 to 4 times the rated speed
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ECONOMICS OF POWER GENERATION
1.
Load factor during a period is
A.
Average load
C.
Average load
Installed
capacity
B.
D.
Maximum load
Installed capacity
Maximum load
Average Load
2.
For economy in generation power
A. load factor should be high
B. diversity factor should be high
C. plant utilization factor should be high
D. load factor and diversity factor should be low
3.
A load curve is a plot of
A. load versus time
C. load versus current
B. load versus cost of power
D. load versus generation capacity
4.
During which season the load on a power plant supplying power to a city will be highest?
A. rainy season
B. summer
C. winter
D. autumn
5.
During summer months the increased load is due to
A. increased water supply
B. vacations in institutions
C. increased business activities
D. increase used of fans and air conditioners
6.
Load due to a ceiling fan is nearly
A. 40 to 50 W
C. 250 to 2000 W
B. 10 W
D. 100 to 200 W
7.
Which domestic utility item has highest power rating?
A. electric iron
B. ceiling fan
C. mixi
D. refrigerator
8.
A power plant supplying energy to a city will usually experience peak demand
A. from midnight to early morning
B. 8 AM to 12 noon
C. 2 PM to 6 PM
D. 6 PM to 12 PM
9.
The
ratio
A.
C.
Maximum demand of the
installation Sum of individual
maximum demand
demand factor
diversity factor
is known as
B. plant use factor
D. plant capacity
factor
10. Capital cost per MWh is the highest in case of
A.
C.
steam power plant
nuclear power plant
B. diesel engine power plants
D. hydroelectric power plant
11. A diesel power plant is best suited as
A. standby plant
C. peak load plant
B. base load plant
D. general purpose plant
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ECONOMICS OF POWER GENERATION
12. A gas turbine power plant usually suits for
A. peak load operation
C. casual run
B. base load operation
D. none of the above
13. Which power plant cannot have single unit of 100 MW?
A.
C.
hydroelectric power plant
steam power plant
B. diesel power plant
D. nuclear power plant
14. The useful life of a diesel engine in a power plant is expected to be
A.
C.
five years
fifty years
B. one year
D. fifteen years
15. Which of the following plants is expected to have the longest expected life?
A.
C.
steam
diesel
B. hydroelectric
D. all have equal life
16. For a power plant the expenditure on which of the following items is expected to be negligible?
A.
B.
publicity
wages
B. taxes
D. insurance
17. At break-even point
A.
C.
constant expenses = profits
total sales = total expenses
B. total sales = variable expenses
D. variable expenses – profits = total sales
18. A nuclear power plant is invariably used as a
A. base load plant
C. standby plant
B. peak load plant
D. spinning reverse plant
19. Efficiency is secondary consideration in case of
A.
C.
base load plants
peak load plants
B. both peak load and base load plants
D. none of the above
20. Which of the following plants will take least time in starting from cold conditions to full load
operation?
A. gas turbine
C. nuclear power plant
B. steam power plant
D. hydroelectric power
plant
21. During load shedding
A.
C.
system voltage is reduced
system power factor is changed
B. some loads are switched off
D. system frequency is reduced
22. Which statement about the daily load curve is valid?
A.
B.
C.
D.
The area under the curve gives the average demand.
The ratio of the area under the curves to the total area of rectangle in which it is
contained gives the load factor for the day.
The peak of the curve gives the installed capacity of the plant.
The area of the curve divided by the number of houses gives load factor
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ECONOMICS OF POWER GENERATION
23. An equipment purchased for $10,000 two years ago has a market value of $1,250 at present. It can
be concluded that
A. The value has depreciated according to straight-line method.
B. The value has depreciated according to diminishing value method.
C. The value has depreciated according to sinking fund method.
D. The value has depreciated with time.
24. In a steam power plant, which component needs maximum maintenance attention?
A.
boiler
B.
condenser
C.
turbine
D. water treatment plant
25. A certain plant has fixed cost of $40,000 and a salvage value of $4,000 at the end of a useful life
of 20 years. The depreciated value of the plant at the end of 10 years will be least (interest rate
being 6% compounded annually) when calculated by
A. Diminishing value method
B. Sinking fund method
C. Straight-line method
D. Sum-of-years digits method
26. In problem 25, the value will be highest when calculated by
A Straight-line method
C. Sinking fund method
B. Diminishing value method
D. Sum-of-years digits method
27. When a power plant is not be able to meet the demand of consumers it will resort to
A.
B.
C.
D.
load shedding
efficient plant operation
power factor improvement at the generators
penalizing high load consumers by increasing the charges of electricity
28. Load shedding is possible through
A.
C.
switching off the loads
voltage reduction
B. frequency reduction
D. any of the above
29. Ideally depreciated value of the plant plus the accumulation is the depreciation fund should be
equal to
A. sinking fund
C. salvage value
B. original invested capital
D. obsolescence rate
30. In power plant, insurance cover is provided for
A.
C.
equipment only
unskilled workers only
B. skilled workers only
D. all of the above
31. Which of the following relation is incorrect?
A.
B.
C.
D.
Capacity factor = Utilization factor x Load factor
Load factor x Maximum load = Average load
Demand factor x Connected load = Maximum demand
None of the above
32. Sinking fund is
A.
B.
C.
D.
Initial value – Salvage value
Capital cost – Operating cost
Periodical maintenance – Breakdown maintenance
Capital cost
USeful life
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ECONOMICS OF POWER GENERATION
33. A low utilization factor for a plant indicates that
A.
B.
C.
D.
plant is used for base load only
plant is under maintenance
plant is used for standby purpose only
plant is used fro peak load as well as base load
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TRANSMISSION AND DISTRIBUTION
1.
Which of the following is usually not the generating voltage?
A. 11 kV
B. 13.2 kV
C. 9.9 kV
D. 6.6 kV
2.
The fact that a conductor carries more current on the surface as compared to core is known as
A. corona
B. permeability
C. unsymmetrical fault
D. skin effect
3.
Transmission efficiency increases as
A. voltage and power factor both decrease
B. voltage and power factor both increase
C. voltage increases but power factor decreases
D. voltage decreases but power factor increases
4.
Skin effect is proportional to
A. (diameter of conductor)2
C. (diameter of conductor)3
B. diameter of conductor
D. (diameter of conductor)1/2
5.
The surge impedance for overhead line is taken as
A. 50-60 ohms
B. 1000-2000 ohms
C. 10-20 ohms
D. 100-200 ohms
6.
The effect of corona is
A. increased reactance
C. increased energy loss
B. increased inductance
D. all of the above
7.
The current drawn by the line due to corona losses is
A. non-sinusoidal
B. sinusoidal
C. square
D. triangular
8.
Presence of ozone as a result of corona is harmful because
A. it gives bad odor
B. it transfers energy to the ground
C. reduces the power factor
D. it corrodes the material
9.
For 66 kV lines, the number of insulator discs used is
A. 8
B. 12
C. 5
D. 3
10. Wooden poles for supporting transmission lines are used for voltages up to
A.
22 kV
B.
440 kV
C.
11 kV
D. 66 kV
500 ohms
D. 50 ohms
11. The surge impedance of transmission lines is about
A.
100 ohms
B.
250 ohms
C.
12. For transmission lines, the standing wave ratio is the ratio of
A.
B.
C.
D.
maximum current to minimum voltage
maximum voltage to minimum voltage
maximum reactance to minimum reactance
peak voltage to rms voltage
13. For a distortionless transmission line (G = shunt conductance between two wires)
A.
RL = GC
B.
RG = LC
C.
RLGC = 0
D.
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14. A relay used in long transmission line is
A.
C.
reactance relay
mho’s relay
B. impedance relay
D. no relay is used
15. The power transmitted will be maximum when
A. sending end voltage is more
C. reactance is high
B. receiving end voltage is more
D. corona losses are least
16. Surge impedance of transmission line is given by
A.
B.
L
C.
1
CL
D.
CL
17. Stages in the provision of electrical energy to a consumer are:
A.
B.
C.
D.
generation and transmission
generation, distribution and transmission
generation, dissipation and distribution
generation, transmission and distribution
18. The purpose of a grid system is to
A.
B.
C.
D.
interconnect the power stations
supply energy to remote areas
make extra high voltage available to consumers
make distribution of energy at reasonable cost
19. Line loss of a transmission line for a given power is
A.
B.
C.
D.
directly proportional to supply voltage and power factor
inversely proportional to supply voltage and power factor
directly proportional to supply voltage and inversely proportional to power factor
directly proportional to power factor and inversely proportional to supply voltage
20. The volume of copper required for a transmission line to transmit a given power is
A.
B.
C.
D.
directly proportional to supply voltage and power factor
inversely proportional to supply voltage and power factor
directly proportional to supply voltage and inversely proportional to power factor
directly proportional to power factor and inversely proportional to supply voltage
21. For a given current density, the resistance voltage drop per line is
A. constant
C. increase with voltage decrease
B. increase with voltage increase
D. remain constant for all voltages
22. The percentage voltage drop of transmission line of question 21 will
A. increase with voltage increase
C. increase with voltage decrease
B. decrease with voltage increase
D. remain constant for all voltages
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23. The efficiency of transmission for a given power improves as
A.
B.
C.
D.
voltage increase and power factor decreases
voltage decreases and power increases
voltage and power factor increase
voltage and power factor decrease
24. Extra high voltages are needed for long distance transmission, transmitting a given power to
reduce the
A. current and cross-sectional area of the line
B. current and the voltage drop
C. voltage drop and cross-sectional area of the line
D. power factor and the voltage drop
25. Various dc and ac systems of transmission are available but to find out which system is superior,
comparison is made on the basis of equal
A. rms voltage between the conductors
B. rms voltage between the conductor and earth
C. maximum voltage between conductors
D. maximum voltage between the conductor and earth
26. Comparison of various overhead transmission systems is made with the
A.
B.
C.
D.
rms voltage between the conductors
rms voltage between the conductor and earth
maximum voltage between conductors
maximum voltage between the conductor and earth
27. For underground cable systems, the comparison is made with the
A.
B.
C.
D.
rms voltage between the conductors
rms voltage between the conductor and earth
maximum voltage between conductors
maximum voltage between the conductor and earth
28. For ac transmission, whether overhead or underground, the most unsuitable system is the
A. 3-phase, 3-wire
C. single phase
B. 3-phase, 4-wire
D. 2-phase, 3-wire
29. Among all the ac systems, the most superior system is
A.
B.
C.
D.
3-phase, 3-wire with maximum voltage between conductors
3-phase, 3-wire with maximum voltage between conductor and earth
3-phase, 3-wire with rms voltage between conductors
3-phase, 3-wire with rms voltage between conductor and earth
30. For overhead transmission line, 3-phase, 3-wire system is
A.
B.
C.
D.
superior over single phase, 2-wire midpoint earthed system
superior over 2-phase, 4-wire system
not superior over the other two
not used in practice
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31. The greatest economy of conductor material is possible by adopting a dc system for transmission,
particularly when the power factor of the ac system is considerably less th an unity. The factor
which limits the dc transmission is
A. no easy way of obtaining high voltage
B. high voltage drop
C. that dc resistance is higher than ac resistance
D. that rms voltage is not available
32. The problems associated with ac transmission system are
A.
B.
C.
D.
high voltage drop, insulation and instability for long lines
continuous loss even at no load, insulation and instability for long lines
continuous load due to charging current, high voltage drop and instability for long lines
continuous loss due to charging current, high voltage drop and insulation
33. The behavior of an ac transmission line used for power transmission depends upon
A.
B.
C.
D.
alternating electrostatic field, resistance and length of the line
alternating electrostatic field, alternating electromagnetic field and length of the line
alternating electromagnetic field, resistance and length of the line
resistance, alternating electrostatic field and alternating electromagnetic field
34. Short transmission lines have a length not exceeding
A.
40 kilometers B.
20 kilometers
C. 80 kilometers
D. 100 kilometers
35. One of the line parameter which is neglected in short transmission line is
A.
capacitance
B.
inductance
C. resistance
D. admittance
36. For a receiving end current I and lagging power factor angle Ψ, the sending e nd voltage Vs for a
short transmission line is
A. Vs = Vr + IX cos Ψ + IR sin Ψ
C. Vs = Vr – IR sin Ψ + IX cos Ψ
B. Vs = Vr – IX cos Ψ + IR sin Ψ
D. Vs = Vr – IR cOs Ψ + IX sin Ψ
37. The term
includes the use of cable and associated control and protective equipment
necessary for supplying electrical energy to required positions on consumer’s premises
A. generation
B. transmission
C. distribution
D. generation and distribution
38. A low tension distribution system consists of
A.
B.
C.
D.
transmission lines, transformers and circuit branches
feeders, distribution and service mains
feeders, transformers and distributors
transmission line, distributors and circuit breakers
39. A feeder in a distribution system is designed primarily from the point of view of
A.
B.
C.
D.
voltage drop
current carrying capacity
voltage drop and current carrying capacity
load capacity
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40. The supply undertaking is allowed to vary the actual voltage at the consumers terminal
A.
B.
C.
D.
because ac supply alternates during each cycle
because of the voltage drop along the distributor
owing to large load at the consumer end
owing to variation of power factor along the distributor
41. The consumer main switch gear is usually located
A.
C.
in the center of the house
over the kitchen sink
B. out of reach
D. at the intake position
42. For the same amount of power to be delivered to a consumer, if the supply voltage is increased to
n times, the size of the feeder cable is
A.
reduced to
C. reduced
to
times
1
n−
1
times
B.
increased to n times
D. increased to n – 1 times
43. If the voltage of a distribution cable is increased to n times, then for the same power and
percentage voltage drop new resistance R of the same length of the distribution in terms of the old
resistance R will be
A. R1 = R/n2
B. R1 = n2R
C. R1 = R/n
D. R1 = nR
44. The weight of the copper required for the new distributor of question 42 will be
A.
C.
increased to n2 times
reduced to n times
B. increased to n times
D. reduced to 1/n2 times
45. In spite of the advantages of increasing voltage for distribution, the limiting factors are:
A.
B.
C.
D.
disproportionately greater cost of higher voltage cables and supplied to a consumer must
be at consumer voltage
voltage drop and the cost of higher voltage cable
the power loss and cost of the higher voltage cable
the power loss and voltage drop
46. A 3-wire dc system of distribution is preferred to a 2-wire dc system because it
A.
B.
C.
D.
results in a saving of copper and has less resistance
results in a saving of copper and makes two alternative voltage available
has less resistance and results in less voltage drop
makes two alternative voltage available and results in less voltage drop
47. The two types of distribution systems used are
A.
C.
radial and delta
ring main and radial
B. radial and star
D. ring main and delta
48. The advantage of the ring main system is
A.
C.
less voltage drop in the feeders
less costly
B. continuity of supply to feeding points
D. none of the above
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49. To reduce the voltage drop at a particular feeding point or load, the system preferred is
A.
B.
C.
D.
ring main
radial
interconnected
radial arrangement superimposed
50. For a given loading, it is better to feed radial distributor at both ends as this gives
A.
B.
C.
D.
minimum loss and voltage drop
greater cross-sectional area of the conductor and minimum loss
continuity of supply and greater cross-sectional area of the conductor
greater cross-sectional area of the conductor and minimum voltage drop
51. For a 3 wire d.c. distributor fed at one end, if the total voltage drop in the neutral is positive it is
A.
B.
C.
D.
added to the negative drop
deducted from the positive drop
added to the positive drop and deducted from the negative drop
deducted from the positive drop and added to the negative drop
52. With point loads in a distributor fed at both ends, in order to determine the maximum voltages
drop it is necessary to know the point of
A. largest load
C. maximum voltage
B. minimum voltage
D. least load
53. At the point of the minimum potential in a distributor fed from both ends, the load at the point is
A.
B.
C.
D.
supplied from the left hand feeding point
supplied from the right hand feeding point
supplied from the left and right hand feeding points
minimal
54. To determine the distribution of load at the point of the minimum potential, the moments in
ampere meters about the one of the feeding point
the moments in ampere meters about the
other feeding point,
A. should be less than
B. should be greater than
C. could be equal to
D. must be equal to
55. For a.c. distributors, the power factor of the load has to be taken into consideration and the
calculations became cumbersome. The approximate method that gives results with in plus or minus
5 percent of the actual voltage drop involves calculating
A. the center of gravity of the load and average power factor
B. the center of gravity of the load, the point of minimum potential and average power factor
C. the center gravity of the load, resistance and reactance per double run and average power
factor
D. the average power factor, the point of minimum potential and resistance and reactance per
double run
56. Voltage drop in a uniformly loaded distributor fed at one end is calculated by assuming the whole
of the load concentrated at
A. middle point
C. the far end of the feeding point
B.
D.
feeding point
distance from the feeding point
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57. Uniformly loaded distributor fed at equal potentials from both ends is treated like the distributor
of question 37 because the voltage drop is
A. approximately halved
B. exactly halved
C. equal to the two feeding points
D. different at the feeding points
58. In actual practice, the potential at the two feeding points is unequal. To calculate the voltage
drop, the difference in potential is
A. added to the actual voltage drop
B. subtracted from the actual voltage drop
C. converted into ampere meters and added to the moments of the higher feeding point
D. converted into ampere meters and moments of the lower feeding point start from this
initial value
59. There should be no break in the neutral, which is usually earthed at the supply end, of a 2 wire a.c.
distribution system because
A. it would make all part dead
B. excess current protection would be affected
C. the action of switching will be nullified
D. it would affect the voltage
60. Commercial premises usually but some domestic installations have 3 phase, 4 wire distribution
system because
A. the supply tariff is cheaper
B. there services are cheaper to install
C. the load is relatively large
D. the voltage drop is less
61. The economical section of the feeder can be obtained by applying
A. Ohm’s law
c. Lenz’s law
B. Faraday’s law
D. Kelvin’s law
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ILLUMINATION
1.
The study of illumination involves
A. design of lighting system
B. study of lighting and wiring system
C. calculations of wiring sizes for various lighting fixtures
D. study of photometry and its application
2.
Energy radiated continuously in the form of lighting waves is called
A. luminous intensity
B. lumen
C. luminous flux
D. illumination
3.
The luminous flux emitted in unit solid angle by a uniform point source having a luminous intensity
of 1 candela is called
A. lumen
B. lux
C. illumination
D. luminance
4.
The luminous intensity is defined as
A. Lumen per square meter
B. Luminous flux per unit solid angle
C. Illumination per square meter
D. Candela per unit solid angle
5.
The luminous intensity of the lamp is expressed in
A. watts
B. lumens
C. lux
D. candela
6.
The illumination at the point of the surface is the luminous flux per unit area of the surface and its
unit is
A. lux
B. lumen
C. candela
D. candela power
7.
Polar curve of a filament lamp
A. shows the distribution of illumination in all directions
B. shows the luminous intensity in all directions in one plane around a light source
C. determine the efficiency of the lamp
D. gives the effectiveness of the reflector used for a lamp
8.
When the light distribution from a lamp or a lamp and fitting is non-uniform the correct value of
the luminous intensity in the particular direction is
A. give the inverse law
B. given the sine law
C. given by the average value
D. taken from the polar curve
9.
The illumination of a surface is
A. directly proportional to the distance of the source
B. inversely proportional to the distance of the source
C. directly proportional to the square of the distance of the source
D. inversely proportional to the square of its distance from the source
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ILLUMINATION
10. The illumination of a surface at any point is proportional to the
the normal at that point and the direction of the luminous flux.
A. sine
B. cosine
C. tangent
of the angle between
D. cotangent
11. The first object of a lighting system is to provide adequate illumination on the working surface. For
proper design the effects of the surroundings must be taken into account and the factors are
A. finish of windows, proportions of room and temperature
B. finish of ceiling and walls, proportion of room, and place of work
C. color of ceiling and walls, proportion of room and window space
D. height of light fittings, room temperature and color of ceiling and walls
12. To use lumen method of design, you must first find
A.
B.
C.
D.
room index and the lumens
room index and then coefficient of utilization
light distribution from a polar curve and then coefficient of utilization
coefficient of utilization and then room index
13. Maintenance factor or depreciation factor takes account of
A.
B.
C.
D.
effects of duct, dirt and fall in light output of the lamp during its life
depreciation in capital cost of installation
effects of dust, dirt and the type of lamp used
condition of the room and the type of lamp used
14. Typical values of maintenance factors range about
for good maintenance conditions down to
for dirty conditions with poor maintenance and cleaning.
A. 0.9, 0.6
B. 0.8, 0.6
C. 0.6, 0.5
D. 0.8, 0.4
15. Total lumens output from lamps when new is equal to
A.
total lumens required x coefficient of utilization
B.
maintenance factor
coefficient of utilization x maintenance factor
C.
D.
total lumens required
total lumens required x maintenance factor
total lumens required
maintenance factor x coefficient of utilization
16. Another requirement of a good lighting scheme is that it makes the principal object the brightest
thing in the field of vision. An illumination ratio of 10 : 3 : 1 has been suggested as the best for
A. background/task/surroundings
B. task/background/surroundings
C. background/surroundings/task
D. surroundings/background/task
17. The lumen output of a 230-volt, 100 watts gas field lamp is approximately
A.
700
B.
1000
C.
1200
D. 1500
18. The principle of working of a high pressure mercury vapour lamp is that
A.
B.
C.
D.
the radiation from the discharge excites a fluorescent material
the radiation is produced directly by the discharge
the radiation is produced by the argon gas
very high voltage is needed to start the discharge
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