a c fundamentals circuits and circuit theory MCQs – Page 5

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
81. The frequency of an alternating current is____________?
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A. the number of waves passing through a point in one second

B. the speed with which the alternator runs

C. the number of electrons passing through a point in one second

D. the number of cycles generated in one minute

82. Power factor of electric bulb is__________?
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A. leading

B. zero

C. unity

D. lagging

83. The phosphors for which of the following pair are 180 out of phase for VL, VC and VR______?
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A. Vc and VR

B. Vc and VL

C. none of the above

D. VL and VR

84. Which of the following waves has the highest value of peak factor ___________?
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A. Sine wave

B. Square wave

C. Triangular wave

D. Half wave rectified sine wave
85. In a purely inductive circuit__________?
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A. none of above is zero

B. actual power is zero

C. apparent power is zero

D. reactive power is zero

86. Time constant of a circuit is the time in seconds taken after the application of voltage to each___________?
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A. 63% of maximum value

B. 25% of maximum value

C. 90% of the maximum value

D. 50% of maximum value

87. Magnitude of current at resonance in R-L-C circuit________?
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A. depends upon the magnitude of L

B. depends upon the magnitude of R, Land C

C. depends upon the magnitude of C

D. depends upon the magnitude of R
88. Time constant of a capacitive circuit__________?
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A. increases with the decrease of capacitance and decrease of resistance

B. increases with the increase of capacitance and decrease of resistance

C. increase with increase of capacitance and increase of resistance

D. increases with the decrease of capacitance and increase of resistance

89. Which of the following circuit component opposes the change in the circuit voltage ?
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A. Resistance

B. Inductance

C. Conductance

D. Capacitance
90. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will__________?
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A. be reduced by half

B. be reduced to one fourth

C. be four times at high

D. be doubled

91. In a R-L-C circuit_________?
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A. all above are correct

B. exchange of power takes place between capacitor and supply line

C. exchange of power takes place between inductor and supply line

D. power is consumed in resistance and is equal to I R

E. exchange of power does not take place between resistance and the supply line

92. Ohm is unit of all of the following except___________?
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A. capacitance

B. resistance

C. capacitive reactance

D. inductive reactance

93. At _______ frequencies the parallel R-L circuit behaves as purely resistive
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A. low

B. high

C. very high

D. very low

94. A parallel AC. circuit in resonance will__________?
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A. have current in each section equal to the line current

B. have a high impedance

C. have a high voltage developed across each inductive and capacitive section

D. act like a resistor of low value

95. Skin effect occurs when a conductor carries current at_______ frequencies
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A. very low

B. medium

C. high

D. low

96. Which of the following coil will have large resonant frequency __________?
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A. A coil with large distributed capacitance

B. A coil with large resistance

C. A coil with low resistance

D. A coil with low distributed capacitance

97. The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is__________?
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A. 12 kW

B. 22 kW

C. 64 kW

D. 32 kW
98. All definitions of power factor of a series R-L-C circuit are correct except__________?
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A. ratio of net reactance and impedance

B. ratio of W and VA

C. ratio of kW and kVA

D. ratio of J and Z

99. The ratio of active power to apparent power is known as factor__________?
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A. demand

B. power

C. load

D. form

100. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is_________?
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A. 8 kVAR

B. 6 kVAR

C. 4 kVAR

D. 16 kVAR