a c fundamentals circuits and circuit theory MCQs – Page 4

Practise focused a c fundamentals circuits and circuit theory questions with marked answers for exam preparation and subject revision.

a c fundamentals circuits and circuit theory Mcqs

61. The inductance of a coil can be increased by_________?
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A. increasing core length

B. choosing core material having high relative permeability

C. decreasing the number of turns

D. decreasing the diameter of the former

62. In an AC. circuit, a low value of kVAR compared with kW indicates_________?
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A. low efficiency

B. maximum load current

C. high power factor

D. unity power factor

63. In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of__________?
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A. LorC

B. C only

C. L only

D. R only

E. R,LorC

64. In AC. circuits, laminated iron is invariably used in order to__________?
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A. increase heat radiation

B. make assembly cheap and easier

C. reduce circuit permeability

D. reduce eddy current loss

65. Inductance of coil___________?
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A. becomes zero with the increase in supply frequency

B. increases with the increase in supply frequency

C. decreases with the increase in supply frequency

D. is unaffected by the supply frequency

66. The time constant of a series R-C circuit is given by____________?
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A. RC2

B. R/C

C. R2C

D. RC

67. In a parallel R-C circuit, the current always________the applied voltage?
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A. leads

B. lags

C. none of the above

D. remains in phase with

68. In a series L-C circuit at the resonant frequency the__________?
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A. impedance is maximum

B. current is maximum

C. voltage across C is minimum

D. current is minimum

69. The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of____________?
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A. increase in temperature

B. skin effect

C. capacitive effect between adjacent coil turns

D. iron loss in core

70. In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will__________?
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A. be four times as high

B. be doubled

C. be reduced by half

D. be reduced to one fourth

71. The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC. will be___________?
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A. 111 V

B. 141.4 V

C. 282.8 V

D. 100 V

72. If a sinusoidal wave has frequency of 50 Hz with 30 A r.m.s. current which of the following equation represents this wave_________ ?
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A. 84.84 sin 25 t

B. 60 sin 25 t

C. 30 sin 50 t

D. 42.42 sin 3141

73. Aphasoris________?
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A. a line which represents the magnitude and phase of an alternating quantity

B. an instrument used for measuring phases of an unbalanced 3-phase load

C. a line representing the magnitude and direction of an alternating quantity

D. a coloured tag or band for distinction between different phases of a 3-phase supply

74. A pure inductance connected across 250 V, 50 Hz supply consumes 100 W. This consumption can be attributed to_________?
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A. the current flowing in the inductor

B. the statement given is false

C. the big size of the inductor

D. the reactance of the inductor

75. The equation of 50 Hz current sine wave having r.m.s. value of 60 A is____________?
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A. 60 sin 50 t

B. 60 sin 25 t

C. 84.84 sin 3141

D. 42.42 sin 314 t

76. Which of the following statements pertains to resistors only _____________?
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A. can act as energy storage devices

B. oppose sudden changes in voltage

C. can dissipate considerable amount of power

D. connecting them in parallel increases the total value

77. Which of the following refers to a parallel circuit ?
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A. The current through any one element is less than the source current

B. The equivalent resistance is greater than any one of the resistors

C. The voltage across element is in proportion to its resistance value

D. The current through each element is same

78. In a three-phase supply floating neutral is undesirable because it way give rise to___________?
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A. high voltage across the load

B. low voltage across the load

C. minimun voltage across the load

D. unequal line voltages across the load

79. Wire-wound resistors are unsuitable for use at high frequencies because they_______?
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A. exhibit unwanted inductive and capacitive effects

B. create more electrical noise

C. consume more power

D. are likely to melt under excessive eddy current heat

80. Capacitive susceptance is a measure of__________?
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A. a purely capacitive circuits ability to resist the flow of current

B. the extent of neutralisation of reactive power in a circuit

C. a purely capacitive circuits ability to pass current

D. reactive power in a circuit

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