1. Which of the following Transformer can have tap changer?
(a) Current transformer.
(b) Potential transformer.
(c) Power transformer.
(d) Earthing transformer.
(a) Current transformer.
(b) Potential transformer.
(c) Power transformer.
(d) Earthing transformer.
Answer
C
2. The degree of mechanical vibrations produced by the lamination of a transformer depends on
(a) tightness of clamping.
(b) gauge of laminations.
(c) size of laminations.
(d) all of the above.
(a) tightness of clamping.
(b) gauge of laminations.
(c) size of laminations.
(d) all of the above.
Answer
D
3. When the square wave is given to primary to a transformer then secondary will gives
(a) no waveform.
(b) square waveform.
(c) pulse waveform.
(d) sine waveform.
(a) no waveform.
(b) square waveform.
(c) pulse waveform.
(d) sine waveform.
Answer
C
4. The efficiency of two identical transformers under loaded conditions can be determined by
(a) short-circuit test.
(b) back-to-back test.
(c) open circuit test.
(d) any of the above.
(a) short-circuit test.
(b) back-to-back test.
(c) open circuit test.
(d) any of the above.
Answer
B
5. Which of the following special transformer is used to convert unbalanced signal to balanced signal?
(a) Isolation transformer.
(b) Auto transformer.
(c) Balun.
(d) Center tapped transformer.
(a) Isolation transformer.
(b) Auto transformer.
(c) Balun.
(d) Center tapped transformer.
Answer
C
6. When the iron losses of a distribution transformer decreases, then its all day efficiency
(a) decreases.
(b) increases.
(c) unaffected
(d) none of the above.
(a) decreases.
(b) increases.
(c) unaffected
(d) none of the above.
Answer
B
7. The main purpose of using core in a transformer is to
(a) decrease iron losses.
(b) prevent eddy current loss.
(c) eliminate magnetic hysteresis.
(d) decrease reluctance of the common magnetic circuit.
(a) decrease iron losses.
(b) prevent eddy current loss.
(c) eliminate magnetic hysteresis.
(d) decrease reluctance of the common magnetic circuit.
Answer
D
8. The functions of using stepped core in transformer is to reduce
(a) hysteresis losses.
(b) eddy current losses.
(c) volume of copper.
(d) reluctance of core.
(a) hysteresis losses.
(b) eddy current losses.
(c) volume of copper.
(d) reluctance of core.
Answer
C
9. When the transformer is loaded then the secondary terminal voltage will fall for
(a) lagging power factor.
(b) unity power factor.
(c) leading power factor.
(d) lagging and leading power factor.
(a) lagging power factor.
(b) unity power factor.
(c) leading power factor.
(d) lagging and leading power factor.
Answer
A
10. Which part of the transformer is most affected by the overheating?
(a) winding of transformer.
(b) winding insulation.
(c) transformer core.
(d) transformer tank.
(a) winding of transformer.
(b) winding insulation.
(c) transformer core.
(d) transformer tank.
Answer
B
11. In a star-delta transformer, the delta side phase voltage leads the star sides phase voltage by an angle
(a) + 30°.
(b) + 45°.
(c) – 30°.
(d) – 45°.
(a) + 30°.
(b) + 45°.
(c) – 30°.
(d) – 45°.
Answer
A
12. Minimum voltage regulation occurs when the power factor of the load is
(a) unity.
(b) lagging.
(c) leading.
(d) zero.
(a) unity.
(b) lagging.
(c) leading.
(d) zero.
Answer
C
13. The chemical used in breather of a transformer should have property of
(a) absorbing heat.
(b) ionizing air.
(c) absorbing moisture.
(d) cleaning oil.
(a) absorbing heat.
(b) ionizing air.
(c) absorbing moisture.
(d) cleaning oil.
Answer
C
14. The power transformer can be termed as a constant
(a) voltage device.
(b) current device.
(c) power device.
(d) main flux device.
(a) voltage device.
(b) current device.
(c) power device.
(d) main flux device.
Answer
D
15. In a transformer, which of the following losses are zero?
(a) Hysteresis losses.
(b) Eddy current losses.
(c) Copper losses.
(d) Frictional and windage losses.
(a) Hysteresis losses.
(b) Eddy current losses.
(c) Copper losses.
(d) Frictional and windage losses.
Answer
D
16. If the input frequency of a transformer is increases then its secondary induced emf
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
Answer
A
17. The main purpose of using shell type transformer is to reduce
(a) hysteresis losses.
(b) eddy current losses.
(c) magnetic leakage.
(d) size of transformer.
(a) hysteresis losses.
(b) eddy current losses.
(c) magnetic leakage.
(d) size of transformer.
Answer
C
18. A transformer has full load copper losses of 600 watt, the copper losses at half load will be
(a) 150 watt.
(b) 300 watt.
(c) 600 watt.
(d) 1200 watt.
(a) 150 watt.
(b) 300 watt.
(c) 600 watt.
(d) 1200 watt.
Answer
A
19. A transformer has 400 watt iron losses at full load, the iron loss at half load will be
(a) 100 watt.
(b) 200 watt.
(c) 400 watt.
(d) 800 watt.
(a) 100 watt.
(b) 200 watt.
(c) 400 watt.
(d) 800 watt.
Answer
C
20. A Buchholz relay can be installed on
(a) auto-transformers.
(b) air-cooled transformers.
(c) oil cooled transformers.
(d) any of the above.
(a) auto-transformers.
(b) air-cooled transformers.
(c) oil cooled transformers.
(d) any of the above.
Answer
C
21. Which of the following electrical machines have maximum efficiency?
(a) Induction motor.
(b) DC motor ultimate.
(c) Power transformer.
(d) Alternator.
(a) Induction motor.
(b) DC motor ultimate.
(c) Power transformer.
(d) Alternator.
Answer
C
22. Harmonics in transformer result in
(a) increased core losses.
(b) increased I2R losses.
(c) magnetic interference with communication circuits.
(d) all of the above.
(a) increased core losses.
(b) increased I2R losses.
(c) magnetic interference with communication circuits.
(d) all of the above.
Answer
D
23. While performing open circuit test on a transformer, the primary is supplied with
(a) rated voltage.
(b) rated current.
(c) reduced voltage.
(d) over voltage.
(a) rated voltage.
(b) rated current.
(c) reduced voltage.
(d) over voltage.
Answer
A
24. Which winding of the transformer has less cross-sectional area?
(a) primary winding.
(b) secondary winding.
(c) low voltage winding.
(d) high voltage winding.
(a) primary winding.
(b) secondary winding.
(c) low voltage winding.
(d) high voltage winding.
Answer
D
25. With the increase in magnitude of the leakage flux, the magnitude of main flux in the core of transformer is
(a) increases.
(b) decreases.
(c) remain unchanged.
(d) none of the above.
(a) increases.
(b) decreases.
(c) remain unchanged.
(d) none of the above.
Answer
B
26. The effect of leakage flux in transformer will result in
(a) more copper losses.
(b) more voltage drop.
(c) less copper losses.
(d) less voltage drop.
(a) more copper losses.
(b) more voltage drop.
(c) less copper losses.
(d) less voltage drop.
Answer
B
27. When a given transformer is run at its rated voltage but reduced frequency, its
(a) flux density remains unaffected.
(b) iron losses are reduced.
(c) core flux density is reduced.
(d) core flux density is increased.
(a) flux density remains unaffected.
(b) iron losses are reduced.
(c) core flux density is reduced.
(d) core flux density is increased.
Answer
D
28. Which of the following device is used to take up the expansion of oil due to temperature rise?
(a) Breather.
(b) Conservator tank.
(c) Radiator.
(d) Buchholz relay.
(a) Breather.
(b) Conservator tank.
(c) Radiator.
(d) Buchholz relay.
Answer
B
29. Which of the following 3-phase connection of a transformer causes interface with the neighboring communication line?
(a) star-delta.
(b) delta-star.
(c) delta-delta.
(d) star-star.
(a) star-delta.
(b) delta-star.
(c) delta-delta.
(d) star-star.
Answer
D
30. Ferrite core are used in high frequency transformers because it has
(a) high specific gravity.
(b) high resistance.
(c) low resistance.
(d) low permeability.
(a) high specific gravity.
(b) high resistance.
(c) low resistance.
(d) low permeability.
Answer
B
31. The selection of distribution transformer is based on
(a) efficiency.
(b) voltage regulator.
(c) all day efficiency.
(d) none of the above.
(a) efficiency.
(b) voltage regulator.
(c) all day efficiency.
(d) none of the above.
Answer
C
32. Which of the following material is used for the construction of a transformer core?
(a) Hardrawn copper.
(b) Silicon steel.
(c) Rought iron.
(d) Soft iron.
(a) Hardrawn copper.
(b) Silicon steel.
(c) Rought iron.
(d) Soft iron.
Answer
B
33. The primary voltage of an isolation transformer is ______ its secondary voltage.
(a) higher than
(b) smaller than
(c) same as
(d) none of the above
(a) higher than
(b) smaller than
(c) same as
(d) none of the above
Answer
C
34. A transformer oil must be free from
(a) sludge.
(b) moister.
(c) gases.
(d) dust.
(a) sludge.
(b) moister.
(c) gases.
(d) dust.
Answer
B
35. As the number of turns of secondary winding increases, then its secondary current of a transformer is
(a) increases.
(b) decreases.
(c) remain same.
(d) all of the above.
(a) increases.
(b) decreases.
(c) remain same.
(d) all of the above.
Answer
B
36. The main reason for generation of harmonics in a transformer could be
(a) fluctuating load.
(b) poor insulation.
(c) mechanical vibrations.
(d) saturation of core.
(a) fluctuating load.
(b) poor insulation.
(c) mechanical vibrations.
(d) saturation of core.
Answer
D
37. Two transformer operating in parallel will share the load depending on their
(a) leakage reactance.
(b) rating.
(c) efficiency.
(d) per unit impedance.
(a) leakage reactance.
(b) rating.
(c) efficiency.
(d) per unit impedance.
Answer
D
38. Which of the following is not a routine test on transformers?
(a) Core insulation voltage test.
(b) Impedance test.
(c) Radio interference test.
(d) Polarity test.
(a) Core insulation voltage test.
(b) Impedance test.
(c) Radio interference test.
(d) Polarity test.
Answer
C
39. When power transformer is operated at very high frequency then
(a) copper losses will very high.
(b) core losses will very high.
(c) primary will draw large power.
(d) all of the above.
(a) copper losses will very high.
(b) core losses will very high.
(c) primary will draw large power.
(d) all of the above.
Answer
B
40. When the primary winding of a transformer is short circuited, its primary inductance is
(a) decreases.
(b) increases.
(c) remains same.
(d) none of the above.
(a) decreases.
(b) increases.
(c) remains same.
(d) none of the above.
Answer
A
41. The efficiency of a transformer will be maximum when
(a) copper losses are equal to hysteresis losses.
(b) hysteresis losses are equal to eddy current losses.
(c) eddy current losses are equal to copper losses.
(d) copper losses are equal iron losses.
(a) copper losses are equal to hysteresis losses.
(b) hysteresis losses are equal to eddy current losses.
(c) eddy current losses are equal to copper losses.
(d) copper losses are equal iron losses.
Answer
D
42. In a transformer, the amount of copper in the primary as compared to secondary is
(a) less.
(b) more.
(c) about same.
(d) none of the above.
(a) less.
(b) more.
(c) about same.
(d) none of the above.
Answer
C
43. At what condition the voltage regulation of a transformer can be zero?
(a) full-load.
(b) lagging power factor.
(c) leading power factor.
(d) zero power factor.
(a) full-load.
(b) lagging power factor.
(c) leading power factor.
(d) zero power factor.
Answer
C
44. The value of flux in the emf equation a transformer is
(a) average value.
(b) r.m.s. value.
(c) maximum value.
(d) none of the above.
(a) average value.
(b) r.m.s. value.
(c) maximum value.
(d) none of the above.
Answer
C
45. The leakage flux in a transformer depends upon the value of
(a) supply frequency.
(b) core losses.
(c) mutual flux.
(d) load current.
(a) supply frequency.
(b) core losses.
(c) mutual flux.
(d) load current.
Answer
D
46. The turn ratio of a 220 V AC to 24 V AC step down transformer must be
(a) 9.1.
(b) 5.13.
(c) 0.109.
(d) 0.513.
(a) 9.1.
(b) 5.13.
(c) 0.109.
(d) 0.513.
Answer
C
47. Which of the following loss in a transformer is zero even at full load ?
(a) Core loss.
(b) Friction loss.
(c) Eddy current loss.
(d) Hysteresis loss.
(a) Core loss.
(b) Friction loss.
(c) Eddy current loss.
(d) Hysteresis loss.
Answer
B
48. When the full load of a transformer is reduced to half full load, its copper losses are
(a) reduced by half.
(b) reduced by four time.
(c) remain unchanged.
(d) double.
(a) reduced by half.
(b) reduced by four time.
(c) remain unchanged.
(d) double.
Answer
B
49. When the full load of a transformer is reduced to half full load, the iron losses are
(a) reduce by half
(b) reduce by four time
(c) remain same
(d) double
(a) reduce by half
(b) reduce by four time
(c) remain same
(d) double
Answer
C
50. The hum in a transformer is mainly attributed to
(a) load changes.
(b) oil in the transformer.
(c) magnetostriction.
(d) mechanical vibrations.
(a) load changes.
(b) oil in the transformer.
(c) magnetostriction.
(d) mechanical vibrations.
Answer
C
51. In which transformer, the territory winding is used?
(a) star delta.
(b) delta star.
(c) delta delta.
(d) star star.
(a) star delta.
(b) delta star.
(c) delta delta.
(d) star star.
Answer
D
52. A no-load test on a transformer is conducted to determine
(a) core loss.
(b) copper loss.
(c) efficiency.
(d) magnetising current and loss.
(a) core loss.
(b) copper loss.
(c) efficiency.
(d) magnetising current and loss.
Answer
D
53. The primary and secondary winding of an auto-transformer are
(a) electrically coupled.
(b) magnetically coupled.
(c) both of the above.
(d) none of the above.
(a) electrically coupled.
(b) magnetically coupled.
(c) both of the above.
(d) none of the above.
Answer
C
54. The no load current in a transformer lags behind the applied voltage by an angle of about
(a) 180°.
(b) 90°.
(c) 75°.
(d) 30°.
(a) 180°.
(b) 90°.
(c) 75°.
(d) 30°.
Answer
C
55. In the circuit model of transformer the copper loss can be represented as
(a) series resistance.
(b) shunt resistance.
(c) shunt inductance.
(d) series inductance.
(a) series resistance.
(b) shunt resistance.
(c) shunt inductance.
(d) series inductance.
Answer
A
56. The main function of conservator in a transformer is to
(a) provide fresh air to transformer.
(b) supply cooling oil to transformer.
(c) protect the transformer from damage when oil expends due to heating.
(d) absorb moisture from air.
(a) provide fresh air to transformer.
(b) supply cooling oil to transformer.
(c) protect the transformer from damage when oil expends due to heating.
(d) absorb moisture from air.
Answer
C
57. Auto transformer can be good choice if the transformation ratio is
(a) more than one.
(b) near to one.
(c) less than one.
(d) near to zero.
(a) more than one.
(b) near to one.
(c) less than one.
(d) near to zero.
Answer
B
58. Transformer breaths in when
(a) load on it increases..
(b) load on it decreases.
(c) load remains constant.
(d) none of the above.
(a) load on it increases..
(b) load on it decreases.
(c) load remains constant.
(d) none of the above.
Answer
B
59. An ideal transformer does not change
(a) voltage.
(b) power.
(c) current.
(d) all of the above.
(a) voltage.
(b) power.
(c) current.
(d) all of the above.
Answer
B
60. When the leakage flux in a transformer is increases, its secondary induce e.m.f. is
(a) decreases.
(b) increases.
(c) remain same.
(d) none of the above.
(a) decreases.
(b) increases.
(c) remain same.
(d) none of the above.
Answer
A
61. The purpose of using transformer oil is to
(a) provide cooling.
(b) absorb heat.
(c) provide insulation.
(d) all of the above.
(a) provide cooling.
(b) absorb heat.
(c) provide insulation.
(d) all of the above.
Answer
D
62. Negative voltage regulation of transformers indicate that the load is
(a) resistive.
(b) capacitive.
(c) inductive.
(d) all of the above.
(a) resistive.
(b) capacitive.
(c) inductive.
(d) all of the above.
Answer
B
63. If the input frequency of a transformers decreases, its magnetic flux in core will
(a) increases.
(b) decrease.
(c) remain same.
(d) none of the above.
(a) increases.
(b) decrease.
(c) remain same.
(d) none of the above.
Answer
A
64. Which of the following meter is used to measure the iron loss of a transformer?
(a) low power factor wattmeter.
(b) unity power factor wattmeter.
(c) frequency meter.
(d) high power factor wattmeter.
(a) low power factor wattmeter.
(b) unity power factor wattmeter.
(c) frequency meter.
(d) high power factor wattmeter.
Answer
A
65. If the primary of a transformer is connected to a DC supply then
(a) nothing is happened.
(b) core losses are increased.
(c) primary may burn out.
(d) leakage flux is increased.
(a) nothing is happened.
(b) core losses are increased.
(c) primary may burn out.
(d) leakage flux is increased.
Answer
C
66. An isolation transformer has primary to secondary turn ratio of
(a) 1 : 2.
(b) 1 : 1.
(c) 2 : 1.
(d) 1:100.
(a) 1 : 2.
(b) 1 : 1.
(c) 2 : 1.
(d) 1:100.
Answer
B
67. When open circuit test is performed on transformer, the primary is supplied
(a) rated kVA.
(b) rated voltage.
(c) rated current.
(d) full-load current.
(a) rated kVA.
(b) rated voltage.
(c) rated current.
(d) full-load current.
Answer
B
68. Which of the following losses are known as variable losses?
(a) Hysteresis losses.
(b) Eddy current losses.
(c) Copper losses.
(d) Core losses.
(a) Hysteresis losses.
(b) Eddy current losses.
(c) Copper losses.
(d) Core losses.
Answer
C
69. Open circuit test on transformers is conducted to determine
(a) hysteresis losses.
(b) copper losses.
(c) core losses.
(d) eddy current losses.
(a) hysteresis losses.
(b) copper losses.
(c) core losses.
(d) eddy current losses.
Answer
C
70. Short circuit test on transformers is conducted to determine
(a) hysteresis losses.
(b) copper losses.
(c) core losses.
(d) eddy current losses.
(a) hysteresis losses.
(b) copper losses.
(c) core losses.
(d) eddy current losses.
Answer
B
71. In a transformer, the eddy current losses are affected by
(a) frequency.
(b) thickness.
(c) flux density.
(d) all of the above.
(a) frequency.
(b) thickness.
(c) flux density.
(d) all of the above.
Answer
D
72. Which of the following transformer secondary winding is connected to earth?
(a) Potential Transformer.
(b) Current Transformer.
(c) Both C.T. and P.T.
(d) None of the above.
(a) Potential Transformer.
(b) Current Transformer.
(c) Both C.T. and P.T.
(d) None of the above.
Answer
C
73. The permeability of the core of an ideal transformer must be
(a) negative.
(b) zero.
(c) equal to air.
(d) infinite.
(a) negative.
(b) zero.
(c) equal to air.
(d) infinite.
Answer
D
74. The core of a high frequency transformer is sometime made of ferrite because ferrite has
(a) high hysteresis.
(b) high resistance.
(c) high specific gravity.
(d) low permeability.
(a) high hysteresis.
(b) high resistance.
(c) high specific gravity.
(d) low permeability.
Answer
B
75. The secondary side of the current transformer is earthed in order to
(a) reduce losses.
(b) avoid electric shock.
(c) avoid the insulation breakdown.
(d) increase accuracy.
(a) reduce losses.
(b) avoid electric shock.
(c) avoid the insulation breakdown.
(d) increase accuracy.
Answer
C
76. In a transformer, the power factor of no-load current is
(a) high.
(b) unity.
(c) small.
(d) zero.
(a) high.
(b) unity.
(c) small.
(d) zero.
Answer
C
77. The power factor of a power transformer on on-load is nearly
(a) zero.
(b) 0.75.
(c) 0.35.
(d) unity.
(a) zero.
(b) 0.75.
(c) 0.35.
(d) unity.
Answer
D
78. The chemical used in breather is
(a) silica gel.
(b) potassium carbonate.
(c) sodium carbide.
(d) transformer oil.
(a) silica gel.
(b) potassium carbonate.
(c) sodium carbide.
(d) transformer oil.
Answer
A
79. When the leakage flux in a transformer increases, it will decrease the
(a) primary induced emf.
(b) secondary induced emf.
(c) secondary terminal voltage.
(d) all of the above.
(a) primary induced emf.
(b) secondary induced emf.
(c) secondary terminal voltage.
(d) all of the above.
Answer
C
80. While conducting short-circuit test on a transformer which side prefer to be short circuited?
(a) High voltage side.
(b) Low voltage side.
(c) Primary side.
(d) Secondary side.
(a) High voltage side.
(b) Low voltage side.
(c) Primary side.
(d) Secondary side.
Answer
B
81. When the supply frequency of a transformer is increased by double, then its eddy current losses will
(a) double.
(b) four times.
(c) eight times.
(d) remain same.
(a) double.
(b) four times.
(c) eight times.
(d) remain same.
Answer
D
82. While conducting open circuit test on a transformer which side prefer to be open?
(a) High voltage side.
(b) Low voltage side.
(c) Primary side.
(d) Secondary side.
(a) High voltage side.
(b) Low voltage side.
(c) Primary side.
(d) Secondary side.
Answer
A
83. Which winding in a transformer has more number of turns?
(a) LV winding.
(b) HV winding.
(c) primary winding.
(d) secondary winding.
(a) LV winding.
(b) HV winding.
(c) primary winding.
(d) secondary winding.
Answer
B
84. If the secondary voltage of a transformer having turn ratio of 0.1 is 12V, the primary applied voltage must be
(a) 0.12 volt.
(b) 1.2 volt.
(c) 12 volt.
(d) 120 volt.
(a) 0.12 volt.
(b) 1.2 volt.
(c) 12 volt.
(d) 120 volt.
Answer
D
85. Star-star transformers work satisfactorily when load is
(a) unbalanced.
(b) balanced.
(c) fluctuating.
(d) all of the above.
(a) unbalanced.
(b) balanced.
(c) fluctuating.
(d) all of the above.
Answer
B
86. Secondary winding of an auto transformer is also known as
(a) compensating winding.
(b) common winding.
(c) territory winding.
(d) high Voltage winding.
(a) compensating winding.
(b) common winding.
(c) territory winding.
(d) high Voltage winding.
Answer
B
87. The leakage flux in a transformer mainly depends upon
(a) load current.
(b) supply voltage.
(c) supply frequency.
(d) power factor.
(a) load current.
(b) supply voltage.
(c) supply frequency.
(d) power factor.
Answer
A
88. Air core Transformer as compared to iron core Transformer has
(a) more copper losses.
(b) less magnetic losses.
(c) more magnetic losses.
(d) no magnetic losses.
(a) more copper losses.
(b) less magnetic losses.
(c) more magnetic losses.
(d) no magnetic losses.
Answer
D
89. The path of the magnetic flux in transformer should have
(a) high reluctance.
(b) low reluctance.
(c) high resistance.
(d) low resistance.
(a) high reluctance.
(b) low reluctance.
(c) high resistance.
(d) low resistance.
Answer
B
90. The purpose of using CRGO steel for the core of transformer is to reduce
(a) eddy current losses.
(b) hysteresis losses.
(c) copper losses.
(d) all of the above.
(a) eddy current losses.
(b) hysteresis losses.
(c) copper losses.
(d) all of the above.
Answer
B
91. The value of flux involved m the e.m.f. equation of a transformer is
(a) average value.
(b) r.m.s. value.
(c) maximum value.
(d) instantaneous value.
(a) average value.
(b) r.m.s. value.
(c) maximum value.
(d) instantaneous value.
Answer
C
92. The all day efficiency of a transformer is also known as
(a) load efficiency.
(b) power efficiency.
(c) current efficiency.
(d) energy Efficiency.
(a) load efficiency.
(b) power efficiency.
(c) current efficiency.
(d) energy Efficiency.
Answer
D
93. Power transformers are generally designed to have maximum efficiency at
(a) no load.
(b) half load.
(c) near full load.
(d) any load.
(a) no load.
(b) half load.
(c) near full load.
(d) any load.
Answer
C
94. Distribution transformers are generally designed to have maximum efficiency at
(a) no load.
(b) half load.
(c) near full load.
(d) any load.
(a) no load.
(b) half load.
(c) near full load.
(d) any load.
Answer
B
95. In a tap changing transformer, the tapping are provided on
(a) primary side.
(b) secondary side.
(c) high voltage side.
(d) low voltage side.
(a) primary side.
(b) secondary side.
(c) high voltage side.
(d) low voltage side.
Answer
C
96. The noise produced by a transformer is termed as
(a) zoom.
(b) hum.
(c) ringing.
(d) buzz.
(a) zoom.
(b) hum.
(c) ringing.
(d) buzz.
Answer
B
97. The most common method of cooling in a power transformer is
(a) natural air cooling.
(b) air blast cooling.
(c) oil cooling.
(d) any of the above.
(a) natural air cooling.
(b) air blast cooling.
(c) oil cooling.
(d) any of the above.
Answer
C
98. At what load the efficiency of a transformer will be zero?
(a) full load.
(b) half load.
(c) no load.
(d) none of the above.
(a) full load.
(b) half load.
(c) no load.
(d) none of the above.
Answer
C
99. Efficiency of a power transformer is nearly
(a) 50 %.
(b) 80 %.
(c) 98 %.
(d) 100 %.
(a) 50 %.
(b) 80 %.
(c) 98 %.
(d) 100 %.
Answer
C
100. When the load on a transformer is increases, the eddy current is
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
Answer
C
101. When the load on a transformer is increases, the copper losses are
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
Answer
A
102. When the load on a transformer is decreases, the hysteresis losses are
(a) decreases.
(b) increases.
(c) remain same.
(d) none of the above.
(a) decreases.
(b) increases.
(c) remain same.
(d) none of the above.
Answer
C
103. Current transformers are also known as
(a) series transformers.
(b) parallel transformers.
(c) auto transformers.
(d) isolation transformers.
(a) series transformers.
(b) parallel transformers.
(c) auto transformers.
(d) isolation transformers.
Answer
A
104. Potential transformers are also known as
(a) series transformers.
(b) parallel transformers.
(c) auto transformers.
(d) isolation transformers.
(a) series transformers.
(b) parallel transformers.
(c) auto transformers.
(d) isolation transformers.
Answer
B
105. Secondary winding of which transformer should never be open circuits when primary is energized?
(a) Auto transformer.
(b) Potential transformer.
(c) Current transformer.
(d) Isolation transformer.
(a) Auto transformer.
(b) Potential transformer.
(c) Current transformer.
(d) Isolation transformer.
Answer
C
106. The primary side and secondary side of a transformer are
(a) electrically linked.
(b) magnetically linked.
(c) conductivity linked.
(d) all of the above.
(a) electrically linked.
(b) magnetically linked.
(c) conductivity linked.
(d) all of the above.
Answer
B
107. A transformer is an electric device which work on
(a) AC.
(b) DC.
(c) both AC and DC.
(d) none of the above.
(a) AC.
(b) DC.
(c) both AC and DC.
(d) none of the above.
Answer
A
108. The main function of a transformer is to change
(a) power.
(b) frequency.
(c) voltage level.
(d) power factor.
(a) power.
(b) frequency.
(c) voltage level.
(d) power factor.
Answer
C
109. The main purpose of transformer cores lamination is to
(a) reduce copper loss.
(b) reduce eddy current loss.
(c) reduce cost.
(d) reduce hysteresis loss.
(a) reduce copper loss.
(b) reduce eddy current loss.
(c) reduce cost.
(d) reduce hysteresis loss.
Answer
B
110. An transformer work on principle of
(a) self-induction.
(b) mutual induction.
(c) coulomb law.
(d) ampere law.
(a) self-induction.
(b) mutual induction.
(c) coulomb law.
(d) ampere law.
Answer
B
111. Transformer are rated in term of
(a) kW.
(b) kWh.
(c) kVA.
(d) kVAR.
(a) kW.
(b) kWh.
(c) kVA.
(d) kVAR.
Answer
C
112. When the supply frequency of a transformer is increases, the iron losses will
(a) decrease.
(b) remain same.
(c) increase.
(d) none of the above.
(a) decrease.
(b) remain same.
(c) increase.
(d) none of the above.
Answer
C
113. The transformer laminations are insulated from each other by
(a) mica strip.
(b) paper.
(c) cotton.
(d) thin coat of varnish.
(a) mica strip.
(b) paper.
(c) cotton.
(d) thin coat of varnish.
Answer
C
114. The main purpose of using Scott connection in 3 phase transformer is to transform
(a) single phase to three phase.
(b) three phase to single phase.
(c) three phase to two phase.
(d) single phase to two phase.
(a) single phase to three phase.
(b) three phase to single phase.
(c) three phase to two phase.
(d) single phase to two phase.
Answer
C
115. Secondary winding of which transformer is kept always closed?
(a) Auto-transformer.
(b) Power transformer.
(c) Potential transformer.
(d) Current transformer.
(a) Auto-transformer.
(b) Power transformer.
(c) Potential transformer.
(d) Current transformer.
Answer
D
116. When the transformer are connected in parallel with incorrect polarity, it will results in
(a) poor power factor.
(b) open circuit.
(c) dead circuit.
(d) higher core loss.
(a) poor power factor.
(b) open circuit.
(c) dead circuit.
(d) higher core loss.
Answer
C
117. The core used in high frequency transformer is usually
(a) copper core.
(b) cost iron core.
(c) air core.
(d) mild steel core.
(a) copper core.
(b) cost iron core.
(c) air core.
(d) mild steel core.
Answer
C
118. Transformer will operates on its maximum efficiency when copper losses are _____ iron losses.
(a) less than
(b) equal to
(c) greater than
(d) none of these
(a) less than
(b) equal to
(c) greater than
(d) none of these
Answer
B
119. The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be
(a) 6400 W.
(b) 1600 W.
(c) 800 W.
(d) 400 W.
(a) 6400 W.
(b) 1600 W.
(c) 800 W.
(d) 400 W.
Answer
D
120. In the circuit diagram of a transformer, the core losses can be taken as
(a) series resistance.
(b) shunt resistance.
(c) series inductance.
(d) shunt inductance.
(a) series resistance.
(b) shunt resistance.
(c) series inductance.
(d) shunt inductance.
Answer
B
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