Electronics and Communication Engineering - Exam Questions Papers

1.
In the signal flow graph of figure below, the gain C/R will be :
11/9
22/15
24/23
44/23
Explanation:

Forward path gain

P1 = 2 x 3 x 4 ⇒ 24, P2 = 5, D1 = 1

D2 = - 3, L1 = - 2, L2 = - 3, L3 = - 4

Two non touching loop = L1 x L3 = - 2 x - 4 = 8

But if we take loop L4 into consideration then = 5 x -1 x - 1 x - 1 = -5

.

2.
The resonant frequency of the circuit shown in figure is,
1/22p Hz
1/2p Hz
1/4p Hz
1/2p Hz
Explanation:

Leq = L1 + L2 + 2M

Leq = 1 + 2 + 2 x = 4 H

.

3.
A short grounded vertical antenna has a length L which is 0.05λ at frequency f. If its radiation resistance at f is R ohms, then its radiation resistance at a frequency 2f will be
R/2Ω
2RΩ
4RΩ
Explanation:

Rr = 80p2

Rrf2.

4.
Which of the following is a solution to the differential equation ?
x(t) = 3e-t
x(t) = 2e-3t
x(t) = 3t2
Explanation:

log x(t) = 3t

x(t) = K.e-3t

Thus option (B) satisfies the solution.

5.
In the circuit shown, the device connected to Y5 can have address in the range
2000 - 20FF
2D00 - 2DFF
2E00 - 2EFF
FD00 - FDFF