Electronics and Communication Engineering - Exam Questions Papers

1. 

Px(X) = M exp(- 2 |x|) + N exp(- 3 |x|) is the probability density function for the real random variable X, over the entire x axis. M and N are both positive real numbers. The equation relating M and N is

A.
B.
C. M + N = 1
D. M + N = 3

Answer: Option A

Explanation:

Using property of probability density of Pxdx = 1

[M exp(- 2 |x|) + N exp(- 3|x|)]dx

1 ⇒ .


2. 

The electric field component of a time harmonic plane EM wave travelling in a non magnetic lossless dielectric medium has an amplitude of 1 V/m. If the relative permittivity of the medium is 4, the magnitude of the time-average power density vector (in W/m2) is

A.
B.
C.
D.

Answer: Option C

Explanation:


3. 

The open loop transfer function of a unity feedback control system is given as The phase cross over frequency and the gain margin are respectively.

A. and
B. and
C. and
D. and

Answer: Option A

Explanation:

At phase cross over frequency

-90° - tan- 1 ωT1 - tan- 1 ωcT2 = - p

= 90°

GM = 1/a where a = | G()|ω=ωc

.


4. 

A unity negative feedback closed loop system has a plant with the transfer function and a controller Gc(S) in the feed forward path. For a unit set input, the transfer function of the controller that gives minimum steady state error is

A.
B.
C.
D.

Answer: Option D

Explanation:

so, Gc(s)|s → 0 should be maximum for low error = ∞

Gc(s)|s → 0.


5. 

Find current i.

A. 4/5 A
B. 5/4 A
C. 1.23 A
D. 1.32 A

Answer: Option A

Explanation:

The given circuit can be compared with Wheatstone's Bridge

Req = (10 + 10 + 10) || (10 + 10 + 10) = 30 || 30 = 15 Ω

.


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