Electronics and Communication Engineering - Exam Questions Papers

41. 

In a JK flip-flop, J is connected to Q and K is connected to Q outputs. The JK FF converts into a

A. RS FF
B. D FF
C. T FF
D. Clocked RS FF

Answer: Option B

Explanation:

Both the input is opposit to each other hence it is D FF.


42. 

A point charge of 6 μC is located at the origin, uniform line charge density of 180 nC/m of 8 m length lies along the x axis and a uniform sheet of charge equal to 25 nC/m2 of area p x 42 lies in the z = 0 plane. Calculate total electric flux leaving the surface of sphere of 4 m radius centered at origin.

A. 86.97 μC
B. 8.697 nC
C. 8.697 μC
D. 86.97 nC

Answer: Option C

Explanation:

According to Gauss's law total flux leaving the closed surface is equal to the charge enclosed by the closed surface

Qencl = (6 x 10-6) + (8 x 180 x 10-6) + (p x 42 x 25 x 10-9)

= (6 x 10-6) + (1.44 x 10-6) + (1.257 x 10-6)

= 8.697 μ Coulombs.


43. 

An infinite ladder is constructed with 1 Ω and 2 Ω resistors as shown below. Find i

A. 8.1818 A
B. 0 A
C. 9 A
D. cannot be determined

Answer: Option C

Explanation:

As ladder is infinite

2R + R2 = 2 + 3R

R2 - R - 2 = 0

R = 2 or R = -1

Negative value of R is not possible

R = 2

i = 9 A.


44. 

Consider the matrix The value of ep is

A.
B.
C.
D.

Answer: Option D

Explanation:

find L-1[sI -A]-1

find inverse Laplace transform of the expression.


45. 

Find current flowing through 1 H inductor at t = 0, at which switch 'S' is opened.

A. 0
B. 2
C. 3
D. 5

Answer: Option C

Explanation:

For t = 0+ current in L is

circuit at t = 0+

I is Io = 3 A.