a) phasor
b) vector quantity
c) scalar quantity
d) none of the above
Answer - b
2. The active and apparent powers of an a.c. circuit are equal in magnitude. The circuit power factor is …….
a) 0.707
b) 0.5
c) 0.8
d) 1
Answer - d
3. The power factor of a.c. circuit is ………..
a) 0
b) 1
c) -1
d) none of the above
Answer - b
4. A series resonant circuit magnifies …………
a) voltage
b) current
c) both voltage and current
d) none of the above
Answer - a
5. The Q factor of a coil is given by ……..
a) R/XL
b) I/XL
c) I/R
d) XL/R
Answer - d
6. Dynamic impedance of a parallel tuned circuit is …………
a) L/CR
b) RL/C
c) L/C
d) R/L
Answer - a
7. Power factor of a circuit can be improved by the use of
a) choke coil
b) capacitor
c) induction motor
d) none of the above
Answer - b
8. Wattless current is said of flow when phase angle between voltage and current is
a) 900
b) 00
c) 600
d) 1800
Answer - a
9. In the above question, what is the true power supplied to the circuit ?
a) 9 W
b) 18 W
c) 4.5 W
d) 36.8 W
Answer - c
10. In an R-L series a.c. circuit XL=R. the phase angle is
a) 900
b) 300
c) 450
d) cannot be predicted
Answer - c
11. A 60% lagging power factor implies that the load is
a) inductive
b) capacitive
c) inductive or capacitive
d) resistive
Answer - a
12. The total impedance of a series resonant circuit is
a) purely inductive
b) purely capacitive
c) purely resistive
d) none of the above
Answer - c
13. The power factor of a circuit can be improved by a
a) capacitor
b) resistance
c) inductor
d) none of the above
Answer - a
14. In the above question, the circuit p.f. may become
a) 0.9 lagging
b) 0.85 lagging
c) 0.8 lagging
d) 0.6 lagging
Answer - d
15. A power triangle can provide information about……
a) power factor
b) kVA
c) kVAR
d) all the above
Answer - d
16. One kilowatt hour is equal to…….
a) 36 x 103 J
b) 103 J
c) 36 x 105 J
d) 105 J
Answer - c
17. A heater coil rated at 1000 W, 220 V is connected to 110 V line. Power consumed is…..
a) 250 W
b) 500 W
c) 200 W
d) 400 W
Answer - a
18. A kilowatt hour is the unit of……..
a) energy
b) power
c) electric charge
d) electric current
Answer - a
19. If current in an electric bulb drops by 2%, then power decreases by
a) 2%
b) 4%
c) 1%
d) 16%
Answer - b
20. A 100 W bulb will give heat and light energy of…..
a) 100 J/s
b) 200 J/s
c) 50 J/s
d) 150 J/s
Answer - a
21. A fuse wire is made of……
a) copper
b) tungsten
c) lead-tin-alloy
d) nichrome
Answer - c
22. Lamps used for house lighting are connected in
a) series
b) parallel
c) mixed grouping
d) arbitrary manner
Answer - b
23. An immersion heater is rated 418 W. It should heat a litre of water from 10 0C to 30 10 0C in nearly
a) 100 s
b) 200 s
c) 144 s
d) 400 s
Answer - b
24. By what percentage will the incandescence a lamp decrease if the current drops by 2%?
a) 1%
b) 4%
c) 2%
d) 8%
Answer - b
25. The heater element in an electric iron is made of…….
a) nichrome
b) iron
c) tungsten
d) constantan
Answer - a
26. If R1 and R2 are respectively the filament resistances of 200 W bulb and 100 W bulb designed to operate at the same voltage, then
a) R1 =2 R2
b) R2 = 4 R1
c) R1 =4R2
d) R2 = 2 R1
Answer - d
27. How many calories of heat will approximately be developed in 210 W electric bulb in 5 minute?
a) 15000
b) 1050
c) 63000
d) 8000
Answer - a
28. Two electric lamps of 40 W, each are connected in parallel. The power consumed the combination is
a) 20 W
b) 60 W
c) 80W
d) 100 W
Answer - c
29. A house is served by a 220 V line. In a circuit protected by a fuse market 9 A, the maximum number of 60 W lamps in parallel that can be turned on is
a) 33
b) 44
c) 22
d) 20
Answer - a
30. The current in a 960 W, 240 V heater operated at 200 V is
a) 0.25 A
b) 3/10 A
c) 2.5 A
d) 10/3 A
Answer - d
31. A transformer will work on……….
a) a.c only
b) d.c only
c) a.c as well as d.c
d) none of the above
Answer - a
32. A transformer does not posses ……..changing property.
a) impedance
b) voltage
c) current
d) power
Answer - d
33. An ideal transformer is one which ……….
a) has no losses and leakage reactance
b) does not work
c) has same number of primary and secondary turns
d) none of the above
Answer - a
34. The primary leakage flux links ………
a) primary winding only
b) secondary winding only
c) both primary and secondary windings
d) none of the above
Answer - a
35. The amount of copper in the primary is ……. That of secondary.
a) about the same as
b) greater than
c) smaller than
d) none of the above
Answer - a
36. When load on a transformer is increased, the eddy current ……….
a) is increased
b) remains unchanged
c) is decreased
d) none of the above
Answer - b
37. The approximate efficiency of a large transformer is ………
a) 65%
b) 50%
c) 80%
d) 95%
Answer - d
38. A transformer has 200 W as iron loss at full-load. The iron loss at half full-load will be …….
a) 50 W
b) 100 W
c) 400 W
d) 200 W
Answer - d
39. Transformers having rating less than 5 k VA are generally……..
a) oil cooled
b) natural cooled
c) water cooled
d) none of the above
Answer - b
40. The secondary load impedance of a step-up transformer is Zs the primary impedance Zp will be
a) equal to Zs
b) greater than Zs
c) less than Zs
d) none of the above
Answer - c
41. The power efficiency of a lighting transformer is always……..its all-day efficiency.
a) equal to
b) higher than
c) less than
d) none of the above
Answer - b
42. What is the approximate efficiency of large transformers?
a) 65%
b) 75%
c) 85%
d) 95%
Answer - d
43. The inductive reactance of a transformer depends on
a) e.m.f.
b) m.m.f.
c) leakage flux
d) magnetic flux
Answer - c
44. How are transformers generally cooled for installations rated at less than 5 kVA?
a) oil cooled
b) air cooled
c) water cooled
d) none of the above
Answer - b
45. The transformer that does not provide electric isolation is
a) power transformer
b) autotransformer
c) current transformer
d) potential transformer
Answer - b
46. The advantage of would rotor motor is that ……….
a) it is inexpensive
b) it requires less maintenance
c) external resistance can be inserted in the rotor circuit
d) none of the above
Answer - c
47. The full-load slip of a 3-phase induction motor ranges from ………
a) 10% to 20%
b) 20% to 30%
c) 2% to 5%
d) none of the above
Answer - c
48. In a 3-phase induction motor, the rotor speed is ……. The synchronous speed.
a) greater than
b) smaller than
c) equal to
d) none of the above
Answer - b
49. When the rotor of a 3-phase induction motor is blocked, the slip is ……..
a) zero
b) 0.5
c) 0.1
d) 1
Answer - d
50. When the rotor of a
3-phase induction motor is blocked, the slip is ……..
a) zero
b) 0.5
c) 0.1
d) 1
Answer - d
51. 3-phase wound rotor
motors are also called ……….motors.
a) synchronous
b) slip ring
c) series
d) commutator
Answer - b
52. The stator of a 3-phase induction motor
produces ……… magnetic filed.
a) steady
b) rotating
c) alternating
d) none of the above
Answer - b
53. If a 4-pole induction motor has a
synchronous speed of 1500 r.p.m., then, supply frequency is ……..
a) 50 Hz
b) 25 Hz
c) 60 Hz
d) none of the above
Answer - a
54. The air-gap between stator and rotor of a
3-phase induction motor ranges from ……….
a) 2 cm to 4 cm
b) 0.4 mm to 4 mm
c) 1 cm to 2 cm
d) 4 cm to 6 cm
Answer - b
55. At no-load, the rotor core loss of a
3-phase induction motor is ………
a) large
b) small
c) practically zero
d) none of the above
Answer - c
56. In the slip of induction motor increases,
then, current in the stator winding ……..
a) is increased
b) is decreased
c) remains unchanged
d) none of the above
Answer - a
57. The approximate efficiency of a 3-phase,
50Hz, 4-pole induction motor running at 1350 r.p.m. is ………
a) 90%
b) 40%
c) 65%
d) none of the above
Answer - a
58. For higher efficiency of 3-phase induction
motor, the slip should be ……..
a) large
b) very large
c) as small as
possible
d) 1
Answer - c
59. In an induction motor, the ratio of rotor
Cu loss and rotor input is given by…….
a) s
b) 1/s
c) 1 – s
d) s/1 – s
Answer - a
60. The no-load speed of an induction motor
depends upon…….
a) the supply
frequency
b) the number of its
poles
c) the maximum
flux/phase
d) only (i) and (ii)
Answer - d
61. The supply voltage to an induction motor
is reduced by 1%. By what percentage, approximately, will the maximum torque
decrease?
a) 20%
b) 50%
c) 40%
d) 10%
Answer - a
62. In an induction motor, slip depends
on……..
a) supply frequency
b) rotor input power
c) rotor copper loss
d) (ii) and (iii)
Answer - d
63. The operation of an induction motor is
based on…….
a) Lenz’s law
b) Ampere’s law
c) mutual induction
d) self induction
Answer - c
64. The frequency of rotor current in a
6-pole, 50 Hz, 3-phase induction motor running at 950 r.p.m. is……
a) 2.5 Hz
b) 1.5 Hz
c) 5 Hz
d) 0.05 Hz
Answer - a
65. If the speed of 3-phase induction motor increases, its
efficiency……
a) decreases
b) increases
c) remains the same
d) insufficient data
Answer - b
66. A current of 3 + j 4 amperes is flowing
through a circuit. The magnitude of current is ………
a) 7 A
b) 5 A
c) 1 A
d) 1.33 A
Answer - b
67. In the complex number 4 + j 7, 7 is called
the ……… component…….
a) real
b) imaginary
c) in-phase
d) quadrature
Answer - d
68. The conjugate of -4 + j 3 is …………
a) 4 – j 3
b) -4 – j 3
c) 4 + j 3
d) none of the above
Answer - b
69. For addition or subtraction of phasors, we
use …….. form.
a) polar
b) rectangular
c) trigonometrical
d) none of the above
Answer - b
70. The reciprocal of j is……..
a) j
b) –j
c) j2
d) none of above
Answer - b
71. In the above problem, circuit power factor
is….
a) 0.756 lag
b) 0.525 lead
c) 0.625 lag
d) 0.852 lag
Answer - a
72. In the above question, the value of
inductance is
a) 0.25 H
b) 0.08 H
c) 1.25 H
d) 0.318 H
Answer - d
73. In the above question, what is the power
factor of the circuit ?
a) 0.525 leading
b) 0.803 lagging
c) 0.625 leading
d) 0.325 lagging
Answer - b
74. In
the above question, what is the circuit power factor ?
a) 0.707 lag
b) 0.848 lag
c) 0.515 lag
d) 0.432 lag
Answer - b
75. The a.c. power in a load that is conserved
is…..
a) real
b) reactive
c) apparent
d) all above
Answer - d
76. The question that contains all the power
information in a given load is
a) active power
b) complex power
c) reactive power
d) apparent power
Answer - b
77. If the load p.f. is 75%, then the apparent
power utilized by the load is
a) 37.5%
b) 75%
c) 60%
d) 25%
Answer - b
78. In a power triangle, the side representing
the apparent power (S) lies in the first quadrant. The load power factor is
a) zero
b) unity
c) lagging
d) leading
Answer - c
79. The magnetic material used in permanent
magnets is…….
a) iron
b) soft steel
c) nickel
d) hardened steel
Answer - d
80. The relative permeability of iron is of
the order of……
a) zero
b) 104
c) 1
d) 10-4
Answer - b
81. Which of the following is more suitable
for the core of an electromagnet?
a) soft iron
b) air
c) steel
d) tungsten steel
Answer - a
82. Magnetic flux passes more readily through……
a) air
b) wood
c) vacuum
d) iron
Answer - d
83. The magnetic material used in temporary
magnets is…….
a) hardened steel
b) cobalt steel
c) soft iron
d) tungsten steel
Answer - c
84. Magnetic flux density is a…….
a) vector quantity
b) scalar quantity
c) phasor
d) none of the above
Answer - a
85. When a charged particle moves
through a magnetic field, it suffers a change in……
a) direction
b) speed
c) energy
d) no change
Answer - a
86. The resistance of an ideal ammeter is…….
a) zero
b) high
c) infinite
d) 10
Answer - a
87. The resistance of an ideal voltmeter is…..
a) zero
b) infinite
c) very low
d) data incomplete
Answer - b
88. In the above question, the momentum of the
particle will……
a) be zero
b) change
c) not change
d) none of the above
Answer - b
89. A voltmeter, an ammeter and a cell are
connected in series. The ammeter will
a) be burnt
b) show almost zero
c) give large value
d) cannot say
Answer - b
90. The range of an ammeter can be…..
a) increased only
b) decreased only
c) increased or
decreased
d) information
incomplete
Answer - a
91. A charge will experience a force in an
electric field when it is….
a) stationary
b) moving
c) stationary or
moving
d) none of the above
Answer - c
92. A direct current is sent through a helical
spring. The spring tends…….
a) to get shorter
b) to rotate about the
axis
c) to get longer
d) to move eastward
Answer - a
93. Magnetic field is caused by….
a) stationary charge
b) a moving positive
charge only
c) a moving negative
charge only
d) moving positive and
negative charges both
Answer - d
94. The B-H curve for __________ will be a
straight line passing through the origin
a) air
b) soft iron
c) hardened steel
d) silicon steel
Answer - a
95. When p.f. is improved, the kW capacity of alternators is….
a) increased
b) decreased
c) unaffected
d) none of the above
Answer - a
96. The best located of p.f. correction
equipment to be installed on the transmission line is at the……
a) sending end
b) receiving end
c) middle of line
d) none of the above
Answer - b
97. Arc and induction furnaces operate on……
a) very low lagging
p.f.
b) very low leading
c) very high leading
p.f.
d) none of the above
Answer - a
98. When p.f. at the generating station is
improved, the cost per unit….
a) decreases
b) increases
c) remains same
d) none of the above
Answer - a
99. Most of the loads are…..
a) inductive
b) capacitive
c) resistive
d) none of the above
Answer - a
100. The capital cost of a power plant depends
on……
a) installed capacity
only
b) number of units
only
c) both (i) and (ii)
d) none of the above
Answer - c
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