a c fundamentals circuits and circuit theory MCQs – Page 3

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

41. Form Factor is the ratio of__________?
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A. r.m.s. value/peak value

B. r.m.s. value/average value

C. average value/r.m.s. value

D. average value/peak value

42. If two sine waves of the same frequency have a phase difference of JT radians, then_______?
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A. both will reach their minimum values at the same instant

B. both will reach their maximum values at the same instant

C. when one wave reaches its maximum value, the other will reach its minimum value

D. none of the above

43. Inductance affects the direct current flow__________?
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A. at the time of turning on and off

B. only at the time of turning off

C. at all the time of operation

D. only at the time of turning on

44. If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is____________?
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A. a sinusoid of the same frequency

B. not a sinusoid

C. a sinusoid of half the original frequency

D. a sinusoid of double the frequency

45. A sine wave has a frequency of 50 Hz. Its angular frequency is ________ radian/second.
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A. 5 n

B. 50 jt

C. 100 n

D. 25 JT

46. The phase difference between voltage and current wave through a circuit element is given as 30. The essential condition is that
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A. both waves must have same frequency

B. both waves must have identical peak values

C. both waves must have zero value at the same time

D. none of the above

47. In a loss-free R-L-C circuit the transient current is__________?
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A. non-oscillating

B. square wave

C. oscillating

D. sinusoidal

48. Inductance of a coil Varies__________?
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A. directly as the cross-sectional area of magnetic core

B. inversely as the length of the iron path

C. directly as square of number of turns

D. directly as the permeability of the core

E. as A. to (d)

49. Capacitors for power factor correction are rated in_________?
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A. kVAR

B. kV

C. kW

D. kVA

50. An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms?
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A. the current through the resistance is more

B. the current through the resistance is less

C. both resistance and inductance carry equal currents

D. none of the above

51. Time constant of an inductive circuit___________?
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A. increases with decrease of inductance and increase of resistance

B. increases with decrease of inductance and decrease of resistance

C. increases with increase of inductance and decrease of resistance

D. increases with the increase of inductance and the increase of resistance

52. A heater is rated as 230 V, 10 kW, A.C. The value 230 V refers to__________?
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A. average voltage

B. peak voltage

C. none of the above

D. r.m.s. voltage

53. Capacitive reactance is more when_______?
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A. capacitance is less and frequency of supply is more

B. capacitance is more and frequency of supply is less

C. capacitance is more and frequency of supply is more

D. capacitance is less and frequency of supply is less

54. Power factor of the system is kept high__________?
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A. to reduce voltage regulation of the line

B. to maximise the utilization of the capacities of generators, lines and transformers

C. due to all above reasons

D. to reduce line losses

55. The period of a sine wave is _____ seconds. Its frequency is
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A. 20 Hz

B. 40 Hz

C. 50 Hz

D. 30 Hz

56. In the case of an unsymmetrical alternating current the average value must always be taken over__________?
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A. the whole cycle

B. unsymmetrical part of the wave form

C. the quarter cycle

D. the half cycle

57. Pure inductive circuit takes power from the A.C. line when_________?
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A. applied voltage decreases but current increases

B. applied voltage increases but current decreases

C. both applied voltage and current increase

D. both applied voltage and current decrease

58. In an A.C. circuit power is dissipated in____________?
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A. inductance only

B. none of the above

C. capacitance only

D. resistance only

59. Time constant of an inductive circuit_________?
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A. increases with increase of inductance and decrease of resistance

B. increases with the decrease of inductance and decrease of resistance

C. increases with decrease of inductance and increase of resistance

D. increases with the increase of inductance and the increase of resistance

60. The power is measured in terms of decibles in case of_________?
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A. electronic equipment

B. transformers

C. current transformers

D. auto transformers

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