# Electronics and Communication Engineering - Automatic Control Systems

### Exercise :: Automatic Control Systems - Section 1

21.

In the given figure the input frequency is such that R << Xc, then A. v0 lags vi by 90° B. v0 leads vi by 90° C. v0 and vi are in phase D. either (b) or (c)

Explanation:

Voltage across capacitor lags by 90°.

22.

In the given figure, of potentiometer V0 = Vi (R0/Ri) only when A. RL = 0 B. RL = ∞ C. RL is neither low nor high D. RL is low but not zero

Explanation:

If RL is not infinite, the voltage ratio of potentiometer depends on the value of RL. This is called loading effect.

23.

A unity feedback system has open loop transfer function The closed loop transfer function is

 A. B. C. D. Explanation: .

24.

Bellows converts

 A. pressure difference into displacement B. pressure difference into voltage C. displacement into pressure difference D. either (a) or (c)

Explanation:

To measure pressure, it is convenient to convert pressure into displacement and then use a displacement transducer.

25.

Assertion (A): The steady state response, of a stable, linear, time invariant system, to sinusoidal input depends on initial conditions.

Reason (R): Frequency response, in steady state, is obtained by replacing s in the transfer function by jω

 A. Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D. R is correct but A is wrong