# Electronics and Communication Engineering - Exam Questions Papers

6.
The transfer function Y(s)/R(s) of the system shown is
0
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?
1 wavelength long
0.5 wavelength long
0.6 wavelength long
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
sFs - f(0)
F(t)dt
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 :
0.4
0.757
0.643
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
Q1 and Q0
Q0 and Q1
Q1 Q0 and Q1 Q0
Q1 Q0 and Q1 Q0