# Electronics and Communication Engineering - Exam Questions Papers

41.

The Z-inverse of the given Z-transform is __________ A. unit step B. unit ramp C. unit impulse D. unit parabola

Explanation: value of  x(n) = d(n) impulse response.

42.

Find the Fourier transform of the half cosine pulse as shown below : A. 0.5 {sin c [0.25(f - 1)] + sin c [2.5(f + 1)]} B. 0.5 {sin c [0.5(f - 1)] + sin c [0.5(f + 1)]} C. 0.25 {sin c [0.25(f - 1)] + sin c [0.25 (f - 1)]} D. 0.25 {sin c [0.5(f - 1)] + sin c [0.5(f - 1)]}

Explanation:

The given signal can be expressed as multiplication of x1(t) and x2(t) as shown below.

where A = 2, T/2 = 0.25 => T = 0.5

x(t) = x1(t) x x2(t)

=> X(f) = X1(f) * X2(f)

Now X1(f) = [δ(f - f0) + δ(f + f0)]

= [sin c [T(f - f0)] + sin c[T(f + f0)]] Now, A = 2, T = 0.5 and f0 = = 1

=> X(f) = 0.5[sin c (0.5(f - 1)) + sin c (0.5(f + 1))].

43.

The q-v relation of a capacitor is v = 1 + q + qx. Find the amount of energy required to charge this capacitor from q(t0) = 0 to q(t) = 5 C.

 A. B. C. D. Explanation: 44.

V-I relationship of a network N is given by, V = 8 - 4I. The equivalent circuit to the network N is shown below
The values of IN and RN are A. 0, 2 B. 0, 4 C. 2, 4 D. None of these

Explanation:

Given equivalent circuit is Norton's equivalent circuit

V = 8 - 4I

Put V = 0I = IN = 2 A

Put I = 0 V = VTH = 8 V .

45.

If the open-loop transfer function is a ratio of a numerator polynomial of degree 'm' and a denominator polynomial of degree 'n', then the integer (n - m) represents the number of:

 A. breakaway points B. unstable poles C. separate root loci D. asymptotes