A.C Fundamentals, Circuits and Circuit Theory MCQs

Question 1

Which of the following waves has the highest value of peak factor ?

Accepted Answer

Half wave rectified sine wave

Answer

Square wave

Answer

Sine wave

Answer

Triangular wave

Question 2

In a purely inductive circuit

Accepted Answer

Actual power is zero

Answer

Reactive power is zero

Answer

Apparent power is zero

Answer

None of above is zero

Question 3

Pure inductive circuit takes power from the A.C. line when

Accepted Answer

Applied voltage decreases but current increases

Answer

Applied voltage increases but current decreases

Answer

Both applied voltage and current increase

Answer

Both applied voltage and current decrease

Question 4

The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 ohms. If frequency is increased to 100 Hz, reactance becomes __________ ohms.

Accepted Answer

10

Answer

2.5

Answer

5

Answer

15

Question 5

Time constant of a circuit is the time in seconds taken after the application of voltage to each

Accepted Answer

63% of maximum value

Answer

25% of maximum value

Answer

50% of maximum value

Answer

90% of the maximum value

Question 6

Magnitude of current at resonance in R-L-C circuit

Accepted Answer

Depends upon the magnitude of R

Answer

Depends upon the magnitude of L

Answer

Depends upon the magnitude of C

Answer

Depends upon the magnitude of R, Land C

Question 7

Inductance of a coil Varies

Accepted Answer

All of above

Answer

Directly as the cross-sectional area of magnetic core

Answer

Directly as square of number of turns

Answer

Inversely as the length of the iron path

Question 8

Two waves of the same frequency have opposite phase when the phase angle between them is

Accepted Answer

180°

Answer

360°

Answer

90°

Answer

0°

Question 9

When an alternating current passes through an ohmic resistance the electrical power converted into heat is

Accepted Answer

True power

Answer

Apparent power

Answer

Reactive power

Answer

None of the above