Electronics and Communication Engineering - Exam Questions Papers

26. 

A function n(x) satisfied the differential equation where L is a constant. The boundary
conditions are: n(0) = K and n(∞) = 0. The solution to this equation is

A. n(x) = K exp(x/L)
B. n(x) = K exp (-x/L)
C. n(x) = K2 exp (-x/L)
D. n(x) = K exp (-x/L)

Answer: Option D

Explanation:

n(∞) = 0, B = 0, n(0) = k B = k.


27. 

If over the path shown in the figure is

A. 0
B.
C. 1
D. 23

Answer: Option C

Explanation:

.


28. 

50 independent low pass signals of bandwidth W, 2W, 3W, W, 2W, 3W, W, 2W, 3W Hz are to be time division multiplexer on a common channel using PAM. To achieve this, the minimum transmission capacity of the channel should be __________ .

A. 1 Hz
B. 12 Hz
C. 3 Hz
D. 6 Hz

Answer: Option B

Explanation:

The commulator in TDM has to rotate at a speed twice that of highest bandwidth 3W x 2 = 6W Hz.

Channel capacity = 2B = 2(6 W) = 12 W Hz.


29. 

Find the value of K for which Vy = 0

A.
B.
C.
D.

Answer: Option C

Explanation:


30. 

Two coils X of 1000 turns and Y of 2000 turns are placed such that 60% of the flux produced by coil X links coil Y. A current of 1 A in coil X produces 0.1 wb flux. The mutual inductance between coils is

A. 0.12 H
B. 0.08 H
C. 0.06 H
D. 0.04 H

Answer: Option A

Explanation:

L2 = 0.1 X 4 = 0.4

M = kL1L2 = 0.6 0.4 X 0.1

= 0.6 X 0.2 = 0.12 .