# Electronics and Communication Engineering - Exam Questions Papers

6.

The transfer function Y(s)/R(s) of the system shown is A. 0 B. C. D. Explanation:

Construct a signal flow graph  .

7.

A lossless transmission line with air dielectric is 6 m long. What is the line length at 30 MHz?

 A. 1 wavelength long B. 0.5 wavelength long C. 0.6 wavelength long D. 0.25 wavelength long

Explanation:

V = 3 x 108 m/s for lossless line Line length = = 0.6 wave length long.

8.

Given that F(s) is the one-sided Laplace transform of f(t), the Laplace transform of f(t)dt is

 A. sFs - f(0) B. C. F(t)dt D. Explanation:

Since it is one-sided Laplace transform.

9.

The antenna current of an AM broad cast transmitter, modulated to a depth of 40% by an audio sine wave is 11 amperes. It increased to 12 ampere as a result of simultaneous modulation by another sine wave. The modulation index due to this second sine wave is :

 A. 0.4 B. 0.757 C. 0.643 D. 0.8

Explanation:    μ2 = 0.57057, μ12 + 0.16 = 0.57057

⇒ μ1 = 0.64 .

10.

Two D flip-flop as shown below are to be connected as a synchronous counter that goes through the following Q1Q0 sequence
00 → 01 → 11 → 10 → 00 → __________
The inputs D0 and D1 respectively should be connected as A. Q1 and Q0 B. Q0 and Q1 C. Q1 Q0 and Q1 Q0 D. Q1 Q0 and Q1 Q0 