# Electronics and Communication Engineering - Exam Questions Papers

46.
System is at rest for t < 0. Vs = sin 2t. Determine v(t) for t greater than zero.
Explanation:

KCL at node V

Natural response from s + 2, is Ae-2t

For Vs = sin 2t, s = 2j

Since the system is at rest for t < 0

Now substituting t = 0, we get

47.
A 300 MHz plane EM wave is propagating in free space. The wave is incident normally on an infinite copper slap. The antenuation constant for the wave is (σcopper = 5.8 x 107 mho/ m). The skin depth is
0.005 x 10-3 m
0.0038 x 10-3m
0.0028 x 10-3 m
0.0024 x 10-3 m
Explanation:

.

48.
Following figure represents
AND
OR
NAND
NOT
Explanation:

The output C is low only when A and B are both 1.

49.
For parallel RLC circuit, which one of the following statements is NOT correct?
The bandwidth of the circuit deceases if R is increased
The bandwidth of the circuit remains same if L is increased
At resonance, input impedance is a real quantity
At resonance, the magnitude of input impedance attains its minimum value
Explanation:

Bandwidth =

Thus it is maximum at resonance.

50.
The practical resonant circuit is shown in above figure. Find the expression for the resonant frequency ωo
None of these