A.C Fundamentals, Circuits and Circuit Theory MCQs

Question 1

The form factor is the ratio of

Accepted Answer

r.m.s. value to average value

Answer

Peak value to r.m.s. value

Answer

Average value to r.m.s. value

Answer

None of the above

Question 2

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?

Accepted Answer

220 V

Answer

$$200\sqrt 3 {	ext{ V}}$$

Answer

$$\frac{{200}}{{\sqrt 3 }}{	ext{ V}}$$

Answer

None of the above

Question 3

The period of a sine wave is ___________ seconds. Its frequency is

Accepted Answer

50 Hz

Answer

20 Hz

Answer

30 Hz

Answer

40 Hz

Question 4

The time constant of the capacitance circuit is defined as the time during which voltage

Accepted Answer

Rises to 63.2% of its final steady value

Answer

Falls to 36.8% of its final steady value

Answer

Rises to 38.6% of its final steady value

Answer

None of the above

Question 5

The square waveform of current has following relation between r.m.s. value and average value.

Accepted Answer

r.m.s. value is equal to average value

Answer

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

Answer

r.m.s. value of current is less than average value

Answer

None of the above

Question 6

The r.m.s. value of pure cosine function is

Accepted Answer

0.707 of peak value

Answer

0.5 of peak value

Answer

Same as peak value

Answer

Zero

Question 7

The phosphors for which of the following pair are 180° out of phase for VL, VC and VR?

Accepted Answer

VC and VL

Answer

VC and VR

Answer

VL and VR

Answer

None of the above

Question 8

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

Accepted Answer

282.8 V

Answer

141.4 V

Answer

111 V

Answer

100 V

Question 9

In an AC. circuit, a low value of kVAR compared with kW indicates

Accepted Answer

High power factor

Answer

Low efficiency

Answer

Unity power factor

Answer

Maximum load current