a c fundamentals circuits and circuit theory MCQs – Page 2

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
21. For a frequency of 200 Hz, the time period will be__________?
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A. 0.005 s

B. 0.5 s

C. 0.0005 s

D. 0.05 s

22. In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its half value__________?
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A. will change the resonance frequency

B. will increase the selectivity of the circuit

C. will change the maximum value of current at resonance

D. will change the impedance at resonance frequency

23. The best place to install a capacitor is___________?
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A. any where

B. across the terminals of the inductive load

C. far away from the inductive load

D. very near to inductive load

24. The product of apparent power and cosine of the phase angle between circuit voltage and current is
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A. volt-amperes

B. true power

C. reactive power

D. instantaneous power

25. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_______ohms?
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A. 10

B. 2.5

C. 5

D. 15

26. The time constant of the capacitance circuit is defined as the time during which voltage________?
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A. none of the above

B. falls to 36.8% of its final steady value

C. rises to 63.2% of its final steady value

D. rises to 38.6% of its final steady value

27. The power factor at resonance in R-L- C parallel circuit is________?
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A. zero

B. 0.08 lagging

C. 0.8 leading

D. unity
28. The square waveform of current has following relation between r.m.s. value and average value?
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A. r.m.s. value of current is less than average value

B. r.m.s. value of current is greater than average value

C. none of the above

D. r.m.s. value is equal to average value
29. The voltage of domestic supply is 220V. This figure represents__________?
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A. peak value

B. mean value

C. r.m.s. value

D. average value

30. When an alternating current passes through an ohmic resistance the electrical power converted into heat is__________?
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A. none of the above

B. reactive power

C. true power

D. apparent power

31. In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value of 220 V is induced. Which of the following values is indicated by the voltmeters ______?
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A. 220 V

B. 220/V3 V

C. none of the above

D. 220V3V

32. The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces__________?
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A. the same heat as produced by A.C. when flowing through the same circuit

B. the less heat than produced by A.C. flowing through the same circuit

C. the more heat than produced by A.C. when flowing through the same circuit

D. none of the above

33. The period of a wave is___________?
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A. none of the above

B. the same as frequency

C. time required to complete one cycle

D. expressed in amperes

34. A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to________?
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A. the current flowing in capacitor

B. the size of the capacitor being quite big

C. the capacitive reactance in ohms

D. the statement is incorrect
35. The power consumed in a circuit element will be least when the phase difference between the current and voltage is________?
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A. 90

B. 0

C. 180?

D. 60

36. The transient currents are associated with the____________?
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A. applied voltage to the circuit

B. resistance of the circuit

C. impedance of the circuit

D. changes in the stored energy in the inductors and capacitors
37. Poor power factor________?
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A. overloads alternators, transformers and distribution lines

B. results in all above

C. reduces load handling capability of electrical system

D. results in more voltage drop in the line

E. results in more power losses in the electrical system

38. The r.m.s. value and mean value is the same in the case of___________?
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A. triangular wave

B. square wave

C. half wave rectified sine wave

D. sine wave

39. In a pure resistive circuit__________?
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A. current is in phase with the voltage

B. current leads the voltage by 90

C. current can lead or lag the voltage by 90

D. current lags behind the voltage by 90

40. Power factor of the following circuit will be unity
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A. inductance

B. capacitance

C. resistance

D. both A. and B.