ELECTRICAL ENGINEERS Pre Board Examination
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ELECTRICAL ENGINEERING PROFESSIONAL SUBJECTS
INSTRUCTION: Select the correct answer for each of the following questions. Mark only
one answer for each item by shading the box corresponding to the letter of your
choice on the answer sheet provided. STRICTLY NO ERASURES ALLOWED. Use pencil no. 2
only. Use only scratch paper(s) provided. Use also back page as scratch paper. Do not
detach the staple wire.
1.
When one coil of magnetically coupled pair has a current of 5 A, the resulting
flux Φ11 = 0.4 mWb and flux Φ12 = 0.8 mWB respectively. If the turns are N1 = 500
and N2 = 1500, find the coefficient of mutual inductance.
A.
B.
2.
B.
C.
D.
C. amplifying the high audio frequencies
D. converting the phase modulation to FM
That steady current that will charge a battery at the same rate of the actual
current.
Its average value.
Its peak value.
The steady current that produces the same rate of heating in a resistor as
the actual current.
For transformer losses reduction.
To increase its efficiency.
C. To improve the cooling.
D. For voltage regulation improvement.
Removing bypass capacitor across the emitter-leg resistor in a CE amplifier
causes:
A.
B.
8.
boosting the bass frequency
pre-amplifying the whole audio band
What is the primary function of the tubes welded on the side of oil-type
transformer?
A.
B.
7.
Capacitor reactance is halved
Impedance is doubled
Current amplitude is doubled
The voltage across the capacitor is halved
What is the rms value of an AC current?
A.
6.
C. Decreases
D. First decreases and then increases
A pre-emphasis circuit provides extra noise immunity by:
A.
B.
5.
Increases
Remains constant.
When the amplitude of the oscillator in a series RLC circuit is doubled, the ___.
A.
B.
C.
D.
4.
C. 120 mH
D. 240 mH
For a JFET, when VDS is increased beyond the pinch off voltage, the drain
current:
A.
B.
3.
60 mH
1069 mH
Increase in current gain
Increase in voltage gain
C. Decrease in current gain
D. Decrease in voltage gain
Find the average emf induced in a 500 turns coil if there is a current change if
0.25 A in time of 0.1 s.
A. 1250 V
B. 12.5 mV
C. 125 mV
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D. 125 V
9.
The breakdown mechanism in a lightly doped p-n junction under reverse biased
condition is called: _______.
A.
B.
Avalanche breakdown
Breakdown by tunnelling
C. Zener breakdown
D. High voltage breakdown
10. Positive charge is distributed uniformly throughout a non-conducting sphere. The
highest electric potential occurs ______.
A.
B.
Far from the sphere
Just outside the surface
C. At the surface
D. At the center.
11. In two winding unloaded transformer, the flux linking the primary and secondary
winding are 10 mWb and 8 mWb respectively. What is the coupling coefficient?
A.
0.6
B. 0.9
C. 0.8
D. 0.7
12. Compute for the core loss if the transformer consumes 75 watts when it is
connected across a 240 V source and taking 1.4 A. The primary resistance is 0.25
Ω.
A.
73.6 W
B. 74.65 W
C. 74.75 W
D. 74.51 W
13. In practice, the three phase conductors of a three-phase line are seldom
equilaterally spaced. The usual nonsymmetrical spacing produces unequal
inductances in the three phases, leading to unequal voltage drops and imbalance
in the line. To offset this imbalance, the positions of the conductors are
interchanged at regular intervals in the line. This practice is known as ______.
I.
Transposition
II.
Interchange
A.
B.
Either I or II
Both I and II
C. II
D. I
14. Two loads are connected in parallel. First load takes 200 kVA at 80% lagging
power factor and the second load a pure capacitive load. What is the kVAR of
capacitive load if the total load is 160 kW, unity power factor?
A.
160
B. 120
C. 100
D. 90
15. 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
16. DMC was created by the Energy Regulatory Commission to monitor the compliance of
the distribution utilities to the PDC. DMC stands for ________.
A.
B.
Distribution Market Committee
Distribution Management Committee
C. Distribution Management Commission
D. Distribution Market Commission
17. A rectangular coil of 50 loops is suspended in a field of magnetic induction of
0.65 T. The plane of the coil is parallel to the direction of the field. The
dimensions of the coil are 15 cm perpendicular to the field lines and 12 cm
parallel to them. What is torque acting on it when the current in the coils is 57
A in N-m?
A. 33.3
B. 55.5
C. 66.7
D. 44.4
18. A 4-pole, three-phase 50 Hz induction motor develops a maximum torque of 20 N-m
at 1,440 rpm. Obtain the torque exerted by the motor at 5% slip.
A. 16.51 N-m
B. 17.51 N-m
C. 18.51 N-m
D. 19.51 N-m
19. In a SCR circuit, the angle of conduction can be changed by changing:
A. Anode voltage
B. Forward current rating
C. Anode current
D. Gate current
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20. The current flowing in L and C at parallel resonant are:
A. zero
B. infinite
C. equal
D. different
21. Which of the following statement is CORRECT for Faraday’s law?
A. An induced electromotive
magnetic field.
B. An induced electromotive
electric flux.
C. An induced electromotive
magnetic flux.
D. An induced electromotive
electric field.
force is proportional to the rate of change of
force is proportional to the rate of change of
force is proportional to the rate of change of
force is proportional to the rate od change of
22. Which of the following statement is FALSE?
A.
B.
C.
D.
Interrupts are used to develop RTOS.
RTOS performs tasks in predictable amount of time.
Kernel is the one component of any OS.
Windows 98 is RTOS.
23. Which of the following refers to the power loss due to alternating magnetization
and demagnetization of the core material?
A. No-load loss
B. Hysteresis loss
C. Eddy-current loss
D. Copper loss
24. Four wires meet at a junction. The first carries 4 A into the junction, the
second carries 5 A out of the junction and the third carries 2 A out of the
junction. The fourth carries _____ the junction.
A. 3 A out
B. 3 A into
C. 7 A into
D. 7 A out
25. A transformer has negligible resistance and a p.u. reactance of 0.1. What is its
voltage regulation on full load with a leading p.f. angle of 30°?
A. -10%
B. 10%
C. 5%
D. -5%
26. It is recommended to use UJT oscillator for gate-triggering of the thyristors
mainly because:
A. It is fairly simple.
B. It is less expensive.
C. It provides sharp firing pulses.
D. None of the choices
27. The effective resistance of conductor is increased by ________.
A. skin effect
B. corona effect
C. proximity effect
D. Both skin effect and proximity effect
28. The frequency of the emf in the stator of a 4-pole induction motor is 60 Hz, and
that in the rotor is 2 Hz. At what speed is the motor running?
A. 1,720 rpm
B. 1,740 rpm
C. 1,760 rpm
D. 1,780 rpm
29. A generating station to supply four regions of load whose peak loads are 10 MW, 5
MW, 8 MW, 7 MW. The diversity factor at the station is 1.5 and the average annual
load factor is 60. Calculate the annual energy supplied by the station.
A. 150.12 x 10^6 kWHR
B. 15.012 x 10^6 kWHR
C. 10.512 x 10^6 kWHR
D. 105.12 x 10^6 kWHR
30. Which of the following statement is CORRECT concerning electric field?
A.
B.
C.
D.
Electric field lines may cross.
Electric field point away from a negatively charged particle.
Electric fields are closed together where the field is large.
A charged point particle released from the rest moves along a field line.
31. String efficiency is used for measuring the:
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A. Voltage rating of SCRs.
B. Temperature rating of SCRs.
C. Current rating of SCRs.
D. Degree of utilization SCRs.
32. The skin effect in conductors is due to non-distribution of current in it and
major portion of the current is near the ________ of conductor.
A. surface
B. center
C. axis
D. radial lines
33. An alternator running in parallel with the other alternators all having automatic
voltage regulators is to be taken off the bus. The usual procedure before opening
the switch is to _____________.
A. reduce alternator excitation
B. reduce the power fed to the prime mover
C. increase alternator excitation
D. do nothing
34. Guy wire is used in the construction of distribution lines for what purpose?
A. Providing emergency grounding
B. Support the conductor
C. Supporting the pole
D. Protection against surges
35. How much larger is the rotor reactance of a SCIM at start-up than it is when the
motor operates at 5 percent slip?
A. 20 times
B. 10 times
C. 5 times
D. 25 times
36. Which of the following is NOT part of your unbundling rate in your Meralco
electric bill?
A. Distribution
B. Supplier
C. Transmission
D. Generation
37. A three-phase induction motor is taking 40 kW, the slip being 4%, stator losses
amount to 800 watts, calculate the total power developed.
A. 39.200 kW
B. 40.800 kW
C. 37.632 kW
D. 36.732 kW
38. What characteristic of plates of the battery is where Ampere-hour is rated?
A. Strength
B. Area
C. Distance
D. Thickness
39. When transistors are used in series or parallel, a snubber circuit is used to:
A. Control the current
B. Limit di/dt
C. Control the voltage
D. None of the choices
40. Which of the following has the greatest effect in decreasing the oscillation
frequency of an LC circuit? Using instead _______.
A. L/2 and 2C
B. 2L and C/2
C. 2L and 2C
D. L/2 and C/2
41. A golf ball is struck by a golf club and falls on green three meters above the
tee. The potential energy on the Earth-ball system is greatest _________.
A.
B.
C.
D.
Just
When
When
Just
before the ball is struck
the ball reaches the highest point in its flight
the ball comes to rest on the green
after the ball is struck
42. Name the effect which is resulted because of the size of conductor, frequency,
and the specific resistance of conducting material.
A. Corona effect
B. skin effect
C. proximity effect
D. Thompson effect
43. Power factor of synchronous motor can be made leading by adjusting its:
A. Speed
B. Excitation
C. Supply voltage
D. Supply frequency
44. A permeable substance is one ______________.
A. which is a good conductor
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B. which can behave as a conductor as well as an insulator
C. which is a strong magnet
D. through which the magnetic lines of force can pass very easily
45. A three-phase load draws 250 kW at a power factor of 0.707 lagging from a 44-V
line. In parallel with this load is a three-phase capacitor bank which draws 60
kVA. Find the total current and resultant power factor.
A. 412 A, 0.796 lag
B. 412 A, 0.796 lead
C. 413 A, 0.796 lag
D. 413 A, 0.796 lead
46. The per unit value of 2-ohm resistor at 100 MVA base and 10 kV base voltage is:
A. 4 pu
B. 2 pu
C. 0.5 pu
D. 0.2 pu
47. An inductive load consisting of R and X in series feeding from a 2.4 kV supply
absorbs 288 kW at a lagging power factor of 80%. Determine R and X.
A. R = 21.8 Ω and X = 6.9 Ω
B. R = 12.8 Ω and X = 9.6 Ω
C. R = 9.6 Ω and X = 12.8 Ω
D. R = 18.2 Ω and X = 16.9 Ω
48. In a DC transmission line:
A. It is necessary for the sending end and receiving end to be operated in
synchronism.
B. The effect of inductive and capacitive reactance`s are greater than in an AC
transmission line of the same rating.
C. There are no effects due to inductive and capacitive reactance`s.
D. Power transfer capability is limited by stability considerations.
49. Which of the following protective relay/s operates on the principle of the
Kirchhoff’s Current Law?
A. Overcurrent relay
B. Reverse current relay
C. Undercurrent relay
D. Differential relay
50. In a low-level AM system, amplifiers following the modulated stage must be:
A. linear devices
B. class C amplifiers
C. harmonic devices
D. nonlinear devices
51. An autotransformer is used to connect a 13.2 kV distribution line to a 13.8 kV
distribution line. It must be capable of handling 2000 kVA. There are three
phases connected Y-Y with their neutral solidly grounded. What must be the N C/NSE
turns ratio to accomplish this connection?
A. 24
B. 20
C. 26
D. 22
52. Static VAR compensators are used to control:
A.
B.
C.
D.
Only
Only
Both
None
magnitude of the ac line current form the utility.
the phase of the ac line current from the utility.
magnitude and phase of the ac line current from the utility.
of the choices
53. A series RC circuit is connected with a capacitor and resistor having a voltage
of 60 V and 80 V. What is the total voltage of the circuit?
A. 140 V
B. 100 V
C. 20 V
D. 120 V
54. A 120-V power line is protected by a 15-A fuse. What is the maximum number of
“120-V, 500 W” light bulbs that can be operated at full brightness from this one?
A. 2
B. 4
C. 3
D. 5
55. Find the distance of two identical charges of 4 µC when they experience force of
250 N.
A. 12 mm
B. 5 mm
C. 20 mm
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D. 24 mm
56. A hydroelectric generating station is supplied from a reservoir of capacity
6,000,000 m^3 at a head of 170 m. Assume hydraulic efficiency of 80% and
electrical efficiency of 90%. The fall in the reservoir level after a load of 15
MW has been supplied for 3 hours if the area of the reservoir is 2.5 km^2 is
closest to _________.
A. 5.39 cm
B. 4.32 cm
C. 5.98 cm
D. 4.83 cm
57. A certain amount of fuel contains 15 x 10^10 BTU of energy. What is the
corresponding energy in kilocalories?
A. 3.52 x 10^10
B. 3.25 x 10^10
C. 3.87 x 10^10
D. 3.78 x 10^10
58. In a communication system, noise is most likely to affect the signal:
A. at the transmitter
B. in the information source
C. in the channel
D. at the destination
59. A resistance R and inductive reactance X are connected in parallel across 2.4 kV
RMS absorbs 288 kW at 0.8 power factor. Find the value of R in ohms.
A. 20
B. 30
C. 26.7
D. 45
60. A 230-kV transmission line is sending 100 MW power at 230 kV and 90% power
factor. The impedance is 5 + j20 ohms and its capacitive reactance is -j2500
ohms. Determine the receiving end voltage.
A. 221.72 kV
B. 222.83 kV
C. 226.15 kV
D. 224.28 kV
61. Increasing the voltage of the transmission system to double its original value
with the same power to be transmitted, the new power losses of the transmission
system will be _________ of the original value.
A. twice
B. one half
C. the same
D. one-fourth
62. AC system has the following disadvantages over DC system EXCEPT:
A. line regulation is more
B. charging current exists
C. skin effect exists
D. proximity effect exists
63. Which of the following is the electrical device that is usually required to be
installed in moisture area in the dwelling unit in order to protect the person
from electric shock?
A. Circuit breaker
B. Power Fuse
C. Arc-Fault Circuit Interrupter
D. Ground-Fault Circuit Interrupter
64. A 3-phase, 60 Hz transmission line delivers 20 MVA to a load at 66 kV at 80% p.f.
lagging. The total series impedance of each line is 15 + j75 ohms. If a nominal-π
circuit is used, what would be the transmission efficiency if the admittance is
j0.0006 mhos?
A. 90.8%
B. 91.7%
C. 93.5%
D. 92.6%
65. The value of the resistor creating thermal noise is doubled. The noise power
generated is therefore:
A. halved
B. quadrupled
C. double
D. unchanged
66. GMC was created by the Energy Regulatory Commission to monitor the compliance of
the users of the Grid to the PGC. What does GMC stand for?
A. Grid Market Commission
B. Grid Management Committee
C. Generation Management Corporation
D. Generator Management Committee
67. The output of a 200-volt 1 synchronous motor, taking a current of 20 amperes is 4
HP, its effective armature resistance is 0.5 ohm. The iron and friction losses
amount to 400 watts. What is the motor power factor?
B. 0.896
B. 0.846
C. 0.796
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D. 0.916
68. Calculate the capacitance per kilometer per phase of the single-circuit, twobundle conductor line shown in the figure below. The diameter of each conductor
is 5 cm.
A. 0.126 µF/km
B. 0.0216 µF/km
C. 0.00126 µF/km
D. 0.0126 µF/km
69. Three impedances, Z1 = 6 cis 20°, Z2 = 8 cis 40°, Z3 = 10 are connected in wye and
supplied by a 480 V three phase source. What is the equivalent delta connected
impedance at phase 2?
A. 28.66 + j9.7
B. 22.68 – j0.51
C. 14.17 + j11.35
D. 74.6 + j99.8
70. The boundary of the protection system is determined by the location of
____________.
A. voltage transformers
B. protective relays
C. current transformers
D. circuit breakers
71. A 440 V, 60 Hz, 6 pole, 3-phase induction motor has a rotor input power of 33 kW
at rated voltage and frequency. Under this condition, the rotor emf makes 126
complete cycles/minute. Find the rotor resistance in ohms/phase if the rotor
current is 60 A/phase.
A. 0.011
B. 0.0107
C. 0.107
D. 0.118
72. What is the equivalent value of this expression aj + a^2 in rectangular form?
A. 1.366 – j1.366
B. 1.366 + j1.366
C. -1.366 + j1.366
D. -1.366 – j1.366
73. A car battery is rated at 80 ampere-hour. An ampere-hour is a unit of _____.
A. Power
B. energy
C. charge
D. current
74. A capacitance C is charged through R. The time constant of the charging circuit
is given by:
A. RC
B. 1/RC
C. C/R
D. R/C
75. An inductor motor with 8 poles, 60 Hz is operated with a slip of 3%. Calculate
the rotor speed.
A. 1,684
B. 1,024
C. 873
D. 927
76. A 230-kV transmission line has impedance of 50 cis 78° ohms and a capacitive
reactance of 1200 ohms. It transmits the power of a base load plant. On a certain
dry season, the sending end power is 100 MW at 235 kV and 95% power factor
continuously for a period of one month. If cost of generation is Php 1.30/kWh,
what is the cost of the line losses for the one-month period?
A. Php 565,000
B. Php 12.2 M
C. Php 5.6 M
D. Php 2.3 M
77. A power plant gets water from a dam from a height of 122.45 m at the rate of
1,000 cubic meters per minutes. If the output of the plant is 15,000 kW, what is
the plant efficiency?
A. 80%
B. 75%
C. 70%
D. 65%
78. A light source located 2.75 m from the surface produces an illumination of 528
lux on that surface. Find the illumination in lux if the distance is changed to
1.55 m.
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A. 937
B. 1,298
C. 658
D. 1,662
79. At a DC steady state, capacitor looks like a/an _______ circuit and an inductor
looks like a/an ______ circuit.
A. grounded, shorted
B. shorted, opened
C. opened, shorted
D. opened, opened
80. What does PEMC in EPIRA stand for?
A.
B.
C.
D.
Philippine Energy Market Corporation
Private Energy Marketing Company
Philippine Electricity Market Corporation
Philippine Electrical Marketing Corporation
81. A transfer function is as C(s) = 5/s(s + 5), find the time constant.
A. 5 s
B. 0.1 s
C. 1 s
D. 0.2 s
82. For two alternators operating in parallel, if the load shared by one of the
alternators is to be increased, the field excitation is ____________________.
A.
B.
C.
D.
to
to
to
to
be
be
be
be
strengthened keeping input torque the same
weakened keeping input torque the same
kept constant but input torque should be increased
kept constant but input torque should be decreased
83. Calculate the value of aj+1.
A. 0.5 + j0.866
B. 0.866 – j0.5
C. 1 + j0
D. 0.134 – j0.5
84. A capacitor has an initial charge of 8.3 C. If the current flows through it is
given by the equation i = 2t + 3 A, find the charge when t = 1 s.
A. 16.3
B. 12.3
C. 4
D. 6
85. A 3φ transmission line 200 km long has the following constants: R/φ = 0.16 Ω/km;
X/φ = 0.25 Ω/km; Y/φ = 1.5 × 10–6 S/km. Calculate by rigorous method the sending
end voltage when the line is delivering a load of 20 MW at 0.8 power factor
lagging. The receiving end voltage is kept constant at 110 kV.
A. 121.89 kV
B. 120 kV
C. 117.15 kV
D. 130 kV
86. The direction of induced EMF can be found by ______.
A. Lenz`s Law
B. Fleming`s Right Hand Rule
C. Fleming`s Left Hand Rule
D. Kirchhoff`s Law
87. A 15 hp, 460 V, 60 Hz, 6-pole, 3 phase induction motor has full-load slip of 4%.
Find the full-load torque in N-m.
A. 85
B. 88
C. 93
D. 90
88. In a 13.8 kV, 10 MVA base three-phase system, a phase-to-phase fault occurs. If
the Thevenin’s equivalent impedance of the system is 2.63%, what is the per unit
fault current?
A. 19.01 pu
B. 32.93 pu
C. 57.03 pu
D. 98.78 pu
89. The line current in a three-phase system are Ia = 460, Ib = 0, Ic=4-120, find
the negative sequence current.
A. 12.909-30
B. 2.30930
C. 3.30360
D. 6.91370
90. A transformer is rated 10 kVA, 440/110 V and 60 Hz when operated as conventional
2-winding transformer. This transformer is to be used as 550/440 V step-down
autotransformer in a distribution system. What is the new kVA rating of the
transformer in this manner?
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A. 20
B. 10
C. 37.5
D. 50
91. A wire 100 cm long and carrying current of 40 A is in perpendicular whose
magnetic flux density is 1.5 Wb/m2. Calculate the mechanical power which has
velocity of 5 m/s.
A. 300 W
B. 100 W
C. 150 W
D. 600 W
92. The speed of dc shunt motor can be controlled:
A.
B.
C.
D.
By inserting a resistor in series with armature circuit.
By changing the field resistance.
By changing the terminal voltage applied to armature.
Any of the choices
93. If the torque angle is continuously increasing, the system will become ________.
A. stable
B. oscillatory stable
C. asymptotically stable
D. unstable
94. A wind generator with an efficiency of 80% has a blade diameter of 20 m. If the
wind velocity is 30 km/hr, how much power in kW is obtained from the generator?
A. 58.47
B. 45.78
C. 48.75
D. 54.87
95. What does IEMOP stand for?
A.
B.
C.
D.
Independent Electricity Market Operator of the Philippines
Independent Energy Market Operator of the Philippines
Integrated Electricity Market Operator of the Philippines
Integrated Energy Market Operator of the Philippines
96. What is the reserve capacity, if the maximum demand of generation of power is 50
MW, the load factor of the plant is 60% and the plant capacity factor is 50%?
A. 15 MW
B. 10 MW
C. 20 MW
D. 6 MW
97. The current from neutral to ground connection is 12 A. What is the zero-sequence
component in phase?
A. 12 A
B. 36 A
C. 4 A
D. 3 A
98. In a capacitor the electric charge is stored in:
A. metal plates
B. dielectric
C. dielectric as well as metal plates
D. neither dielectric nor metal plates
99. One primary and one secondary terminal of a two-winding transformer is connected
to an ohm-meter instrument. What will be the reading on this instrument?
A. Impedance is doubled
B. Infinity
C. Zero
D. Equal to winding resistance
100. Given that a transfer function is T(s) = 2/(s – 3), find the system response y(t)
to an input x(t) = u(t), a unit step, assuming zero initial conditions.
A. y(t) = 2/3 - (2/3)e3t
B. y(t) = -2/3 - (2/3)e3t
C. y(t) = 2/3 + (2/3)e3t
D. y(t) = -2/3 + (2/3)e3t
END
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