Electronics and Communication Engineering - Exam Questions Papers

1. 

If X = 1 in the logic equation [X + Z { Y + (Z + X Y)}] { X + Z (X + Y)} = 1, then

A. Y = Z
B. Y = Z
C. Z = 1
D. Z = 0

Answer: Option D

Explanation:

[1 + z{y + z + y}][0 + z] = 1, z = 1, z = 0.


2. 

(22)4 + (101)3 - (20)5 = (x)4 + (4)x+1 where x > 4. The value of x is

A. 6
B. 4
C. 12
D. 8

Answer: Option C

Explanation:

(22)4 + (10)10 - (10)10 = (22)4

Since x > 4, i.e. all the number systems with base greater than 4.

All these will contain symbol '4' which will have same value in all bases.

Converting 4 into base '4'

system (4)10 (10)4

Now (22)4 = (x)4 + (10)4

(x)4 = (22)4 - (10)4 = (12)4

x = 12.


3. 

Consider a system with the transfer function . Its damping ratio will be 0.5 when the value of k is :

A. 2/6
B. 3
C. 1/6
D. 6

Answer: Option C

Explanation:

ξ = 0.5,

We take second term only

.


4. 

For the system with given characteristic equation
s5 + 4s4 + 8s3 + 8s2 + 7s + 4 = 0
The number of roots on left hand side, right hand side and imaginary axis are respectively.

A. 3, 2, 0
B. 4, 0, 1
C. 3, 0, 2
D. 4, 1, 0

Answer: Option D

Explanation:

Apply Routh Hurwitz criteria.


5. 

A series RLC circuit has a resonance frequency of 1 kHz and a quality factor Q = 100. If each of R, L and C is doubled from its original value, the new Q of the circuit is

A. 25
B. 50
C. 100
D. 200

Answer: Option B

Explanation:

Resonant frequency

Quality factor =

where R, L, C all are doubled, then

.


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