WEEKLY EXAM #8 (EE) SET A
1. A bulb having a rating of 220 volts,
75 watts 1s to be connected to a 120
volt source. What power will it draw
of connected across 120 volts source?
A. 15 watts C. 75 watts
B. 12 watts D. 22 watts
2. A parallel plate capacitor with air
between its plates is charged until
the potential difference V appears
across 1t. Another capacitor having
hard rubber (dielectric constant = 3)
between 1ts plates but otherwise
identical, 1s also charged to the
same potential difference. If the
energy of the first capacitor is W,
that of the second 1s
A. OW C. W
B. W/3 D. 3W
3.A 2 -—-henry inductor has 120 turns.
How many turns must be added to raise
its inductance to 3 henrys?
A. 147 turns C. 27 turns
B. 180 turns D. 60 turns
4. A conductor 50 mm log, moves a
velocity of 2.5 meters per second
aCross a magnetic field of
0.90Wb/m”2. What is the voltage
generated?
As UslZo ¥
Ce Uullda ¥
BR. 0.0648 V D. OQ.
072 V
5. 1f a 220 V heater 1s used on 110 V
supply, heat produced by it will be
— as much
A. one-half C. one-fourth
B. twice D. four times
©. Point out the WRONG statement. The
magnetizing force at the center of a
circular coil varies.
. directly as the number of its turns
directly as the current
directly as its radius
inversely as its radius
OQ wm
7. The resistance of a copper wire at
30°C 1s 50 ohms. If the temperature
coefficient of a copper at 0oC is
0.00427°C-1, what 1s the resistance
at 100°C?
A. 72.26 ohms
B. 63.24 ohms
C. 54.25 ohms
D. 58.15 ohms
8. Calculate the induced emf in a 150-
cm? circular coil having 100 turns
when the field strength B passing
through the coil changes from 0.00 to
0.001T in 0.10s at a constant rate
A. 0.005 V Cs. 0.015 ¥
B. 0.010 Vv D. 0.020 V
9. The units of capacitance are
equivalent to:
A. J/C C. Gid
B. V/C D. C2/J
10. A constant current of 5 mA charges a
10pF capacitor for 1 second. How much
1s the voltage across the capacitor
A. S0V CC. 200V
B. 250V D. 1000V
11. Determine the reluctance of a piece
of non-metal of length 150 mm and
cross-sectional area 1800 mm? when
the relative permeability is 4000
A. 15080 A/Wb C. 15872 A/Wb
B. 16380 A/Wb D. 14690 A/Wb
12. A charged capacitor stores 10C at
40V. Its stored energy 1s:
A. 400 J C. 0.23
B. 4 J D. 200 J
13. For a given line voltage, four
heating coils will produce maximum
heat when connected
A. all in parallel
B. all in series
C. with two parallel pairs in series
D. one palr 1n parallel with the other
two in series
14, The resistance of 1.5 km of wire of
cross-sectional area 0.20 mm2 is
15082. DPetermine the resistivity of
the wire in micro-ohm meter
A. 0.02 Cc. 0.017
Be 0:15 De. 0.03
15. A physics instructor in an anteroom
charges an electrostatic generator to
25 pC, then carries it into the
lecture hall. The net electric flux
in N - m*"2/C through the lecture hall
walls 1s:
A. O Co 2od XX 105
B. 25 x 10%=6 D. 2.8 x 1076
16. A 100 turn coil has an inductance of
© mH. If the number of turns is
increased to 300, all other
quantities remaining the same. The
inductance will be
A. 24H C. 54H
B. 12H BEB. 1.5H
17. The torque exerted by an electric
field on a dipole is:
A. parallel to the field and
perpendicular to the dipole moment
B. parallel to both the field and dipole
moment
C. perpendicular to both the field and
dipole moment
D. parallel to the dipole moment and
perpendicular to the field
Page 10f 6
WEEKLY EXAM #8 (EE) SET A
18. Two parallel wires, 4 cm apart,
carry currents of 2A and 4A
respectively, 1n the same direction.
The force per unit length in N/m of
one wire on the other is:
1 x 10-3, repulsive
1 x 10-3, attractive
4 x 10-5, repulsive
4 x 10-5, attractive
19. What 1s the resistance of an open
fuse circuit?
A. at least 1000 ohms
B. infinity
C. zero
D.
100 ohms at standard temperature
20. A wire contains a steady current of
ZA. The number of electrons that
pass a cross section in
28 18;
A. 1.8 x 1019
C. 2.5 x 10%
B. 2.5 x 10¥ BD. 3.9
x 10719
21. A cylindrical copper rod has
resistance R. It 1s reformed to twice
its original length with no change of
volume. Its new resistance 1s:
A. R C. 4R
B. ZR BD. SER
22. A one meter rod of 2 com diameter is
drawn until its resistance is 100
times the 1nitial resistance. Its
length afterward is
A. 10 m C. 100 m
B. 12.5 m D. 5m
23. The four stripes of a resistor are
yellow-violet—-orange—gold. The value
of the resistor should be
A. 470Q, £5% C. 47u%, 15%
B. 47 kQ, +5% D. 4700Q, +10%
24. The total capacitance of two
capacitors is 0.03 pF when joined in
series and 0.16 uF when connected in
parallel. Find the capacitance of
each capacitor.
A. 0.12 uF, 0.04 pF
B. 0.14 pur, 0.06 pF
C. 0.16 ur, 0.08 ur
D. 0.18 ur, 0.10 pF
25. According to Faraday’s Laws of
Electromagnetic Induction, an e.m.f.
1s 1nduced in a conductor whenever it
A. lies in a magnetic field
B. Cuts magnetic rlux
C. moves parallel to the direction of
the magnetic field
D. lies perpendicular to the magnetic
flux.
26. An electron in a television tube has
a charge 1.6 x 107°C and travels at
3 x 107 m/s perpendicular to a flux
density 18.5 uI. Determine the force
exerted on the electron in the field
A. 7.88 x 10-17 N C. 9.88 x 10-17 N
B. 8.88 x 1017" N D. 10.88 x 10-17 N
27. The units of magnetization are:
A. ampere C. ampere -meter”?2
B. ampere ‘meter D. ampere/meter
28. A solenoid is 3.0 cm long and has a
radius of 0.50 cm. It 1s wrapped with
500 turns of wire carrying a current
of 2.0 A. The magnetic field at the
center of the solenoid is:
A. 9.9 = 10*-8 TC, 4.2 x 10-2 T
By, 1.3 ¥ 10°=3 TD, 167
29. 12 volts battery has a 50 ampere-
hour capacity. The internal
resistance is 0.1 ohm. A 5 ohm load
1s connected for 5 hours. How many
ampere—-hours are still left? Select
one:
A. 41.24 C. 38.23
B. 28.51 D.. 39.92
30. A capacitor of 0.0005 uF is to be
formed from tin foils, measuring 3 cm
Xx 1.5 cm. The dielectric to be used
1s 0.5 mm mica film. Determine the
number of tin folls required. The
relative permittivity of mica 1s 4.5.
A. 15 C. 21
B. 18 D.Z4
31. What capacitance must be placed in
series with a 15 uF capacitor to give
a total capacitance of Sur?
A. SUF C. 10UFE
B. 7.5uF D. 15uF
32. An 1solated charged point particle
produces an electric field with
magnitude E at a point Zm away from
the charge. A point at which the
field magnitude is E/4 is:
lm away from the particle
2m away from the particle
4m away from the particle
8m away from the particle
OQ Wx
33. Charge Q 1s distributed uniformly
throughout a spherical insulating
shell. The net electric flux in N
m*2 /C through the inner surface of
the shell 18;
A. 0
EB. Q/eq
C. 20Q/¢o
1x. Q/4m £0
34. What is the normal indication on a
megger when checking insulation?
A one C. middle of scale
B. infinity D. zero
35. Three 3-ohm resistors are connected
to form a triangle. What is the
resistance between any two corners?
A. 3/482 Ce 282
B. 3Q D. 4/3Q
Page 2 of 6
36. A
37
3
A.
B.
39.
4].
42.
wo =
43.
A.
B.
. minimum
WEEKLY EXAM #8 (EE) SET A
positive and negative charge are
4cm apart, when they are moved
together so that they are new 1 cm
apart, the force between them will be
then before
16 times larger C.
8 times larger D.
4 times larger
4 times smaller
Resistors of 200, 20 and 30Q are
connected in parallel. What
resistance must be added in series to
the combination to obtain a total
resistance of 10Q
50 cc. 2.50)
3.50 D. 2Q
Two capacitors Cl and C2 are placed
in series. If Cl= 100 uF, C2= 50 uf,
find the maximum energy stored when
a 220 v dc supply 1s applied across
the combination.
0.107 J C. 0.807 J
0.507 J D. 1.107 J
A 2-T uniform magnetic field makes
an angle of 30 with the z axis. The
magnetic flux through a 3-mZ2 portion
of the xy plane is:
2 .0Wb Cos Ded WD
3.0Wb D. 6.0Wb
. Two long straight wires are parallel
and carry current in the same
direction. The currents are 8.0 and
1ZA and the wires are separated by
0.40 cm. The magnetic field in tesla
at a point midway between the wires
18:
0 C. 8.0 x 10-4
4.0 x 10-4 D. 12 x 10-4
Two long straight wires are parallel
and carry current in opposite
directions. The currents are 8.0 and
1ZA and the wires are separated by
0.40 cm. The magnetic field in tesla
at a point midway between the wires
18:
0 (Ca
4.0 x 10-4
8.0 x 10-4
D. 20 x 10-4
The amplitude modulation generated
at a very low voltage or power
amplifier 1s modulation.
C. high level
D. low level
collector
Two 1dentical coils X and X of 1000
turns each lie in parallel planes
such that 80% of flux produced by one
coil links with the other. If a
current of 5 A flowing in X produces
a flux of 0.05 mWb in it, find the
mutual inductance between X and Y.
8 x 103 H C.
9 x 10-3 H D.
10 x 103 H
11 x 10-3 H
44
A.
B.15606.7 Oersted D.
48.
A.
B.
49.
A.
B.
50.
A.
B.
Ce
D.
21
A.
B.
DL o
Ae
B.
C.
D.
Page 3 of 6
. Determine the emf
If a unit charge is taken from one
point to another over an
equlipotential surface, then
work is done on the charge
work 1s done by the charge
work on the charge is constant
no work is done
1s the minimum number of
over—current device of a lighting and
appliance panelboard that shall be
installed in a cabinet.
16 C. 48
Je D. 24
induced in a coil
of 180 turns when there 1s a change
of flux of 20 mWb linking the coil in
40 ms
100 volts C. 80 volts
90 volts D. 75 volts
. A magnetic circult consists of
silicon steel 3,000 permeability of
10 cm length and cross-section of 1.5
square cm and an air gap of the same
cross-section and of 2 cm length. A
0.5 ampere current flows through 500
turns. What 1s the field intensity at
the air gap?
250 Oersted
C. 795.6 QOersted
2,202 Oersted
An certain resistor dissipates 0.5W
when connected to a 3V potential
difference. When connected to a 1V
potential difference, this resistor
will dissipate:
O0.5W C.
0.167W D.
1.5W
0.056W
How many electrons per second pass
through each section of wire carrying
a current of 0.70 A
1.1 x 1021
GC. 3.
2.1 x 1021 D. 4
dp
Ne
j—t
oO
a
3
Two equally charged spheres repel
each other with a force of 0.1lkg. If
their centers are 20 cm apart, find
the charge on each.
2.09 x 10-6 coul
2.09 x 106 coul
3.00 x 10-6 coul
3.00 2x 106 coul
The mechanical equivalent of heat is
1 cal = 4.18 J. The specific heat of
water 1s 1 cal/g K. An electric
immersion water heater, rated at
400W, should heat a kilogram of water
from 10 C to 30 C in about:
+5 min C. 15 min
1 min D. 45 min
Which of the following is zero
inside a charged conducting sphere?
potential
eleCtric intensity
both (a) and (b)
both (b) and (c)
WEEKLY EXAM #8 (EE) SET A
53. Two electrons 1n a vacuum experience
a force of 2x107-15 N. How far apart
are the electrons?
A. 3.39%10-7m C. 2.84x10-12m
B. 9.60x10-7Tm PD. 35.05% 10~12m
24. Two condensers of capacity 2 F and 3
FF are connected 1n series. A third
condenser of 1 pF 1s connected 1m
parallel to them. The resultant
capacitance is
A. 6 F C. 5/6 F
B. 5/11 F Ds: 11/5 F
55. A magnetic field 1s produced by a
coll of 300 turns which is wound on
a closed iron ring. The ring has a
cross—section of 20 cm? and mean
length of 120 cm. The permeability
of the 1ron 1s 800. Tf the current
in the coil is 10 A, find the energy
stored 1n the magnetic field.
A. 5.7 J Cc. 1.5 J
Bs 0:3 J D. 8.2
So. Let Q denote charge, V denote
potential difference, and U denote
stored energy. Of these quantities,
capacitors 1n parallel must have the
same :
A. Q only Ges U @nly
B. V only D. Q and U only
57. A magnetic field strength of H =
4000A/M is applied to a «circular
magnetic circuit of mean diameter
250mm. If the coil has 500 turns,
find the current in the coil
A. H.BoA C. 6.28A
B. 7.85A D. 11.85A
58. One kWh of electric energy equals
A. 3600 J C. 30600 W
B. 860 kcal D. 4186 J
59. Three capacitors are connected in
series across 135 V supply. The
voltage across them are 30, 45 and 60
and charge on each is 4500 pC. Find
the capacitance of the combination.
21:7 PE Cs 28.0 BF
B. 25.9 uF D. 33.3 uF
*
60. Three equal resistors connected 1n
series across a source of emf
together dissipate 10W of power. What
would be the power dissipated in the
same resistors when they are
connected in parallel across the same
an |
source of emf
A. 10W
B. 30W
C. 90W
D. 270W
6l1.A coil of copper wire has a
resistance of 20 ohms at 18°C if the
temperature coefficient of
resistance of copper at 18°C is 0.004
per LC, determine the resistance of
A. 30.50
the coll when the temperature rises
to 98°C
C. 20.882
B. 26.40 D. 18.60
62. A parallel plate capacitor with
plates of area A that are separated
a distance d by air 1s initially
charged with charge Qc. The energy
stored in the capacitor initially is
FE. The plates are then separated by
2d. What is the new energy stored in
the capacitor?
A. © C. &
Be. 0.5E D. 2E
6S. The eleclric enerqy required to
raise the temperature of a given
amount of water is 1000 kWh. If heat
losses are 25%, the total heating
energy required 1s — kWh.
A. 1500 C. 1333
B. 1250 D. 1000
64. The magnetic field a distance 2 cm
from a long straight current-carrying
wire 1s 2.0 x 10-5 T. The current in
the wire 1s:
A. 0.1l6A Cc. 2.0A
B. 1.0A D. 4.0A
65. The primary function of a fuse is
to
open the circuit
prevent excessive currents
protect the line
. protect the appliance
QW
06. Two coils have inductances of 4 mH
and 9 mH have a coefficient of
coupling of 0.50. If the two coils
are connected 1n series alding, the
total inductance will be
A. 19 mH C. 7 mH
B. 16 mH D. 12 mH
67. A 90 percent electric motor
operating an elevator lifts a 10-ton
load through height of 60 ft.
Calculate the energy required by the
motor to do so
A. 1.81 MJ C. 3.81 MJ
B. 2.81 MJ D. 4.81 MJ
68. Resistor 1 has twice the resistance
of resistor 2. They are
connected 1in parallel to a battery.
The ratio of the thermal energy
generation rate in 1 to that in 2 is:
A. 1 : 4 Ce 1 2 1
B. 1 : 2 BD. 2 2 14
69. Charge 1s placed on the surface of a
Z.7-cm radius isolated conducting
sphere. The surface charge density is
uniform and has the value 6.9 x 107-6
C/m™2. The total charge on the sphere
1S:
A. 9.6 * 10°10 C ©, 4,7 x 107-8 C
B. 2.1 x 10*~8 C D. 6.3 x 10%-8 C
Page 4 of 6
WEEKLY EXAM #8
(EE) SET A
70. A resistance of a4 ohms is connected
across a 1l00V supply. When another
resistor of R’ ohms 1s connected in
parallel with the 4 ohm resistor the
total current taken from the supply
was found to be 50A. The value of the
resistance R’ 1s
A. 4Q C. 3Q
BR. 20 D. 10
71. Determine the mutual inductance
between two colls when a current
changing at 200 A/s in one coil
induces an emf of 2 V in the other
A. 7.5 mH C. 12 mH
B. 10 mH D. 15 mH
72. Two wires made of different
materials Have the same uniform
current density. They carry Lhe same
current only 1f:
A. their lengths are the same
B. their cross-sectional areas are the
same
C. both their lengths and
sectional areas are the same
D. the potential differences across them
are the same
CYOSS—
73. The maximum working flux density of
a lifting electromagnet is 2T and the
effective area of the pole face 1s
circular 1n cross-section. If the
total magnetic flux 1s 400 mWb.
Determine the radius of the pole face
A. 252mm C. 305mm
293mm D. 320mm
us
74. Unit of magnetic flux is
weber C. tesla
ampere—-turn D. coulomb
tw
75. Two parallel plate capacitors A and
B have capacitance of 1 UF and 5 uF
are charged separately to the same
potential of 100V. Now the positive
plate of A plate of A 1s connected to
the positive of B. Find the final
voltage across each capacitor
A. 65.67 volts C. 67.67 volts
B. 06.67 volts D. 68.67 volts
76. A 100w, 100V lamp 1s to be operated
on 250V supply. The walue of
additional resistance to be connected
in series will be
A. 250 Cc. 150
B. 100 PD. ob
77. A copper wire has a resistance of
94.48Q) per 100 meters. What would be
the resistance of 750m of another
wire with four times the cross-
sectional area of the previous wire?
A. 15.7150 C. 17.715Q
B. 16.71582 D., 18.7158
78. A capacitor with a value of C is
connected 1n parallel with a series
combination of 8 and 16 microFarad.
The voltage drop across the capacitor
C 1s 12V . Find the voltage across
the 8 microFarad capacitor.
A. 8V C. 4V
B. 10V Bo, ZN
79. An electron moving with a speed of 5
x 107” m/s at right angle to a magnetic
field of 0.50T. What 1s the radius of
the radius of the circle in which the
electron moves?
A, 3.69 Xx 10+ m C. bh.69 ¥ 1U% m
B. 4.69 x 104m D. 6.69 x 104 m
80. A 120-V power line 1s protected by a
15-A fuse. What 1s the maximum number
of “120V, 500W” light bulbs that can
be operated at full brightness from
this line?
A. 1 CC. 3
B. 2 D. 4
8l. The self inductances of two coils
are 4 mH and 9 mH. If the coefficient
of coupling 1s 0.50, the mutual
inductance between the coils is
A. 12 C. 6.5
B. 3 D. 24
82. Point out of the WRONG statement. In
the node-voltage technique of solving
networks, choice of a reference node
does not
A. affect the operation of the circuit
B. change the voltage across any element
C. alter the p.d. between any pair of
nodes
D. affect the voltages of various nodes
863. A conductor has a area of 40,000 CM.
what 18 the diameter of this
conductor in inches?
A. 0.060 C. 0.50
B. 0.20 D. 0.40
84. A customer OWNS an old alr
conditioning unit rated %*» HP at 70%
efficiency but decided to buy a new
one of the same horsepower rating
with 85%efficiency and with 2 years
warranty. If the usage of new unit 1s
8 hours per day and 150 days per year,
what 1s the differential cost of
energy in one year when the unit cost
of energy is P8.99/kWHR?
A. P9,870 C. P1,014
B. P8,070 D. P2,029
85. A capacitor CC 1s connected in
parallel with a series combination of
capacitors of 10 and 5 micro Farad.
The voltage drop across the capacitor
C is 15 V. The 3 capacitors have been
connected for sometime and have
reached their present value. Find the
voltage across the capacitor with 10
micro F.
A. 8 V C. 20 V
B. 10 Vv D. & V
Page 5 of 6
WEEKLY EXAM #8 (EE) SET A
86. In practice, earth is chosen as a
place of zero electric potential
because it
A. is non-conducting
B. is easily available
C. keeps losing and gaining electric
charge every day
PD. has almost constant potential
87.A circuit, consisting of three
resistances 12 €, 18 €Q and 36 Q
respectively joined in parallel, 1is
connected in series with a fourth
resistance. The whole is supplied at
60 V and it is found that the power
dissipated in the 12 Q resistance is
36 W. Determine the value of the
fourth resistance.
A. 7.36 Q C. 11.33Q
B. 9.54 Q D. 13.72 Q
88. Two batteries emfs at 20V and 21V
respectively and internal
resistances of 0.80 QQ and 0.200
respectively, are connected in
parallel across 5082 resistor.
Calculate the voltage across the load
resistor
A, 10.0V C. 30.6V
B. 20.6V D. 40.6V
89. Vertical clearances of all
service drop conductors above
roofs shall NOT be less than one of
the following values.
A. 2000 mm C. 3000 mm
B. 2750 mm D. 2500 mm
90. Two point charges Q1 and QO; are 3 m
apart and their combined charge 1s 20
BC. If one repels the other with a
force of 0.0715 HN; determine Lhe
charge Q: and Q» in microcoulombs.
fs 2 and 106 C. © and 14
B. 5 and 15 D. 8 and 12
91. A copper conductor with a diameter
of 0.10 inch has a resistance of 1
ohm per 1,000 ft. What is the
resistance of 200 ft copper wire with
a diameter of 40 mils?
1.25 Cc. 1.45
gs De 12d
w >
92. An average emf of 40V is induced in
a coil of inductance 150 mH when a
current of 6A 1s reversed. Calculate
the time taken for the current to
reverse
A. 40 ms C. 50 ms
B. 45 ms D. 55 ms
93. If the length and diameter of a
conductor 1s tripled the resistance
will increased approximately by
2, 1
A. 665% Co. 333%
2 1
1 0 ~0
B. 66 2 Yo D. 333 Yo
94. Two positive point charges 12 x 10-
10 C and 8 x 10-10 C are placed
10 cm apart. Find the work done in
bringing the two charges 4 cm closer.
A. 4.12 x 10-8 J C. 6.85 x 10-8 J
B. 5.76 x 108% J De 7.99 % LU
95. The total negative charge on the
electrons in 1mol of helium (atomic
number 2, molar mass 4)
A. L.2 x 1054€ C. 2.8 X 10°C
B., 1.9 x 10°C D. 0.9 x 10°C
Fr
96. What 1s the total resistance of
eleven 33 kQ resistor connected in
parallel?
A. 33 kO C. 16.5 k&
B. 3 k& D. 11 ke
07. The polarity of an unmarked magnet
can be determined using:
A. a charged glass rod
B. a compass
C. an electroscope
D. another unmarked magnet
98. If dielectric slab of thickness 5 mm
and & = 6 1s 1nserted between the
plates of an air capacitor with plate
separation of 6 mm, 1ts capacitance
18
A. decreased
B. almost doubled
C. almost halved
D. unaffected
99. A parallel-plate capacitor has
plates of area 2 m? spaced by three
slabs oO different dielectric
materials. The relative
permittivities are 2, 3, 6 and
thickness are 0.4, 0.6 and 1.2 mm
respectively. Calculate the combined
capacitance.
A. 1.37 x 10% F
B. 1.83 x 10-¢ F
C. 2.48 x 10-¢ F
D. 2.95 x 10-6 F
100. What type of communication system
uses light rather than electricity o
communicate?
A. data communication
B. optical communication
C. microwave communication
D. fiber optic communication
Page 6 of 6
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