# Electronics and Communication Engineering - Automatic Control Systems

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

16.

First column elements of Routh's tabulation are 3, 5, , 2. It means that there

 A. is one root in left half s plane B. are two roots in left half s plane C. are two roots in right half s plane D. is one root in right half s plane

Explanation:

Since there are two sign changes in the first column, hence two roots in right half plane.

17.

When a unit step voltage drives a lag network the output

 A. remains constant at unit step value B. increases exponentially from zero to final value C. decreases exponentially from 1 to 0 D. either (b) of (c) depending on values of R and C

Explanation:

At t = 0 the capacitor behaves as a short-circuit and output voltage is 0. At t = ∞ capacitor behaves as an open-circuit and V0 = Vi.

18.

For the given figure C(s)/R(s) A. B. C. D. Explanation: .

19.

For the circuit in the given figure,  A. B. C. D. Explanation: .

20.

A system has its two poles on the negative real axis and one pair of poles lies on jω axis. The system is

 A. stable B. unstable C. limitedly stable D. either (a) or (c)