Complex AC MCQs

Question 1

From the Fig. 5.16 it can be concluded that

Accepted Answer

v leads i by n/2

Answer

v lags i by it/2

Answer

v leads i by n

Answer

v lags i by n

Question 2

A coil is connected across a 200 V, 50 Hz supply and takes a current of 10 A. The loss in the coil is 1000 W. The impedance and resistance of the coil are

Accepted Answer

20 12, 10

Answer

10 L-1, 8 S-2

Answer

15 0, 8 L2

Answer

301, 151k

Question 3

In an A.C. circuit (sine wave) with R and L in series

Accepted Answer

the voltage across R lags the voltage across L by 90?

Answer

voltage across and L are 180? out of phase

Answer

the voltage across R leads the voltage across L by 90?

Answer

voltage across R and L are in phase

Question 4

While drawing vector diagram for a series circuit, the reference vector is

Accepted Answer

current

Answer

voltage

Answer

power

Answer

phase angle

Question 5

For a purely resistive circuit the following statement is in correct

Accepted Answer

Power factor is unity

Answer

Work done is zero

Answer

Power consumed is zero

Answer

Heat produced is zero

Question 6

What inductance will give the same reactance as a capacitor of 2 p F when both are at 50Hz?

Accepted Answer

5 H

Answer

10 H

Answer

15 H

Answer

20 H

Question 7

In an A.C. circuit I sin is called

Accepted Answer

any of the above

Answer

active component

Answer

wattless component

Answer

none of the above

Question 8

In a R-L-C circuit the impedance is given by

Accepted Answer

Z = 11112 + (XL - Xc)2

Answer

Z = R+ XL ?Xc

Answer

Z = R - XL + Xc

Answer

Z= ii(R+ XL)2 + Xc2

Question 9

Analternating voltage V = 160 + j 120 V is applied to a circuit and the subsequent current flowing I = -6 + j 15 A. The impedance of the circuit is

Accepted Answer

3.2 - j 12

Answer

12 -j 3.2

Answer

6.4 - j 24

Answer

none of the above