Electronics and Communication Engineering - Exam Questions Papers

11. 

The reduced form of the function
X(E, A, B, C, D) = ∑(0, 1, 2, 3, 4, 7, 8, 9, 10, 12, 15, 16, 17, 18, 19, 20, 23, 24, 25, 26, 28, 31) is

A.
B.
C.
D.

Answer: Option A

Explanation:

X =(A + B + D)(A + B + D) (A + B + C + D)

=(D + A D + B D + AB + A D + A B + B D) (A + B + C + D)

=(D + AB + A B)(A + B + C + D)

.


12. 

Consider the probability density f(x) = ae-b|x| where x is a random variable whose allowable values range from x = - ∞ to x = + ∞. The Cdf (Cumulative distribution function) for x ≥ 0 is :

A.
B.
C.
D.

Answer: Option B

Explanation:

.


13. 

The electric field of uniform plane wave is given by E = 20 sin (2 p x 108t- pz) x + 20 cos (2 p x 108t - pz) y. The corresponding magnetic field is

A.
B.
C.
D.

Answer: Option C

Explanation:

H = Hx + Hy

.


14. 

Find I for circuit shown below

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

Answer: Option C

Explanation:

Mesh Analysis

Apply KVL at loop 2

125i2 - 100i3 = 0 ...(i)

Apply KVL at loop 3

120i3 - 100i2 - 20i1 = 0

i1 = 5A

120i3 - 100i2 - 100 = 0

120i3 - 100i2 = 100 ...(ii)

From (i) 125i2 - 100i3 = 0

...(iii)

Put equation (iii) in eq. (ii)

120i 3 - 100i2 = 100

120 x - 100i2 = 100

150i2 - 100i2 = 100

50i2 = 100

i2 = 2A.


15. 

A n-type silicon sample contains a donor concentration of Nd = 2 x 1016 cm-3. The minority carrier hole lifetime is tp0 = 5 μs. The thermal equilibrium generation rate of hole is:

A. 1.125 x 109 cm-3 s-1
B. 0.625 x 109 cm-3 s-1
C. 4.5 x 109 cm-3 s-1
D. 2.25 x 109 cm-3 s-1

Answer: Option D

Explanation:

Then thermal generation rate

= 2.25 x 109 cm3 S-1 .