Electronics and Communication Engineering - Exam Questions Papers

1. 

8416 - 2A16 is equal to

A. 5A16
B. 4A16
C. 7A16
D. 15A16

Answer: Option A

Explanation:

(2A)16 = (00101010)2

2's complement = 11010110 = (D6)16

(84)16 + (D6)16 ⇒ 1(5A)16 carry discarded ⇒ (5A)16 .


2. 

Calculate the electrostatic force of repulsion between two mica particles at a distance of 10-13 m from each other. Charge on a particle is 3.2 x 10-19 C. (relative permittivity for mica is 5)

A. 1.843 x 10-15 N
B. 9.2 x 10-2 N
C. 14.41 x 10-9 N
D. none of these

Answer: Option D

Explanation:

By Coulomb's law:

Electrostatic force = =

= 18.43 x 10- 3 N.


3. 

An electromechanical closed loop control system has the following characteristics equation :s3 + 6Ks2 + (K + 2)s = 8
where K is the forward gain of the system. The condition for closed loop stability is

A. K = 0.528
B. K = 2
C. K = 0
D. K = -2528

Answer: Option A

Explanation:

s3 + 6ks2 + (k + 2)s + 8 = 0

a0 = 1, a1 = 6k, a2 = k + 2, a3 = 8

Apply R.H. criteria.


4. 

What is the propagation constant for air filled wave guide with dimensions a = 1.59" and b = 0.795" at 4.95 GHz. The wave impedance is

A. 400.94 Ω
B. 562.94 Ω
C. 502.80 Ω
D. 492.80 Ω

Answer: Option B

Explanation:

.


5. 

An antenna array comprises of two dipoles that are separated by wavelength. The dipoles are fed by currents of the same magnitude and 90° in phase. The array factor is:

A. 2 cos - 2 sin
B. 2 cos + 2 sin
C. 2 cos
D. 2 sin

Answer: Option A

Explanation:

Array factor

φ = 90°.


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