Electronics and Communication Engineering - Exam Questions Papers

41. 

Given L[f(t)] = and L[g(t)] = also h(t) = , where, x = then, L[h(t)] = __________ .

A.
B.
C.
D.

Answer: Option A

Explanation:

Now, x =

log x = ejp x log S log x = y,

x = ey

log x = log Sejp

x = Sejp

x = S-1

L[f(t)] = L[f(t)] x L[g(t)].


42. 

The voltage reflection coefficient on a 50 Ω line is 0.7∠30°.
The load impedance is

A.
B.
C.
D.

Answer: Option B

Explanation:

.


43. 

For finding the square root of N using Newton's iterative formula, the correct expression is:

A.
B.
C.
D.

Answer: Option B

Explanation:

f(xn) = (x2n - N).


44. 

For a random variable x following the probability density function, p(x), shown in figure, the mean and the variance are respectively,

A. 1/2 and 2/3
B. 1 and 4/3
C. 1 and 2/3
D. 2 and 4/3

Answer: Option B

Explanation:

The mean x is given by

and the variance is


45. 

VR at t < T, t = ∞

A. 500e-40x104t, 0
B. 100e-40x103t, 0
C. 100e-40x106t, 0
D. 100e-40x104t, 0

Answer: Option D

Explanation:

At t = 0, C1, C2, C3 acts as short.

entire voltage will appear cross R.

At t increases the voltage across the resistance decrease exponentially.

T = RCnet = 10 x 2.5 x 10-6 = 25 μ sec

Initial voltage

VR = V0e-t/RC at t = 0 = 100

= 100 e-t/25x10-6 V.

VR = 100 e-40x104t V.

At t = ∞, VR = 0

The charge C0 will be distributed in C1, C2, C3 and no current will flow.