# Electronics and Communication Engineering - Signals and Systems

### Exercise :: Signals and Systems - Section 1

6.

If and A + B is

 A. B. C. D. Explanation:

7.

A voltage V(t) is a Gaussian ergodic random process with a mean of zero and a variance of 4 volt2. If it is measured by a dc meter. The reading will be

 A. 0 B. 4 C. 2 D. 2

Explanation:

8.

A first order system will never be able to give a __________ response

1. band stop
2. band pass
3. all pass
Choose the correct option

 A. 1, 2, 3 true B. 1 and 3 true, 2 false C. 1, 2 are true 3 is false D. 1, 2 are false, 3 is true

Explanation:

Because to design band pass or band stop, transfer function of must be second order.

9.

In the given figure the ratio T/d is the duty factor. A. True B. False

Explanation: .

10.

If £[f(t)] = F(s), then £[f(t - T)] =

 A. est F(s) B. e-st F(s) C. D. Explanation:

A linear system is one in which the relationship between input and output is linear.

All linear system possess the property of superposition i.e., if input u1 gives output y1 and input u2 gives output y2 then input u1 + u2 will give output y1 + y2.

Superposition implies homogencity i.e., if input u gives output y, then input ku gives output ky where k is a rational number.

In general a system is linear if a transformation T satisfies the relation

T(au1 + βu2) = aT(u1) + βT(u2)

where a and β are constant.