# Electronics and Communication Engineering - Signals and Systems

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

36.

The signal defined by the equations f(t) = 0 for t < 0, f(t) = E for 0 ≤ ta and f(t) = 0 for t > a is

 A. a step function B. a pulse function C. a shifted step function originating at t = a D. none of the above

Explanation:

It is a pulse lasting for t = a.

37.

Inverse Laplace transform of is

 A. 2 exp (- 2.5 t) cosh (0.5 t) B. exp (- 2 t) + exp (- 3 t) C. 2 exp (- 2.5 t) sinh (0.5 t) D. 2 exp (- 2.5 t) cos 0.5 t

Explanation: f(t) = e-2t + e-3t.

38.

Two function g1(t) and g2(t) with correlation of 6 has average power of 4 and 5 respectively. The power of g1(t) + g2(t) is

 A. 9 B. 21 C. 3 D. 15

Explanation:

Power of two correlated signal is P = P1 + P2 +2R1, 2(t).

39.

A box has 4 white and 3 red balls. Two balls are taken out in succession. What is the probability that both are white?

 A. B. C. D. Explanation:

The probability that first ball is white is and the probability the second ball is white is . The probability that both are white is .

40.

Z transform is a non-linear operation.

 A. True B. False