# Online Electronics and Communication Engineering Test - Previous Exam Papers Test 5

Instruction:

• This is a FREE online test. DO NOT pay money to anyone to attend this test.
• Total number of questions : 20.
• Time alloted : 30 minutes.
• Each question carry 1 mark, no negative marks.
• DO NOT refresh the page.
• All the best :-).

1.

What are the values of Emax and Emin displayed on the oscilloscope, when a 1 kV P-P carries is modulated to 50%?

A.
 2 kV, 0.5 kV
B.
 1 kV, 0.5 kV
C.
 0.75 kV, 0.25 kV
D.
 0.5 kV, 1.5 kV

Explanation:

Emax - Emin = 0.5 x 1 kV = 0.5 kV

2Emax = 1.5 kVi, Emax = 0.75 kV

Emin = 0.25 kV.

2.

The equation sin (z) = 10 has

A.
 no real or complex solution
B.
 exactly two distinct complex solutions
C.
 a unique solution
D.
 an infinite number of complex solutions

Explanation:

Since value lies between - 1 and + 1. Therefore no real or complex solution exists.

3.

The logic function f(A B, C) = Σm(0, 2, 4, 5, 6) represented by

A.
 i
B.
 i, ii
C.
 i, iii
D.
 i, ii, iii

Explanation:

4.

In the given figure
.
The damping coefficient for the given circuit is __________ .

A.
 1/2
B.
 1/4
C.
 2
D.
 1

Explanation:

Damping coefficient is given by,

Substituting R = 1 Ω, L = 1 H

.

5.

Find current i.

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

Explanation:

The given circuit can be compared with Wheatstone's Bridge

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

.

6.

The Vs is given by

A.
 8 V
B.
 13 V
C.
 1 V
D.
 4 V

Explanation:

Using Nodal analysis

...(i)

...(ii)

V2 = 2Vx

V2 = 2V ...(iii)

...(iv)

Put V2 = 2V

Put in equation (iii), Vs = 3V1 - V2

Vs = 3 x (+5V) - 2V

Vs = 15V - 2V = 13V.

7.

For the 8085 assembly language program given below, the content of the accumulator after the execution of the program is

A.
 00H
B.
 45H
C.
 67H
D.
 E7H

Explanation:

A → 0100 0101

B → 0100 0101

Carry flag → 0

RAR will A → 0010 0010

XRA B 0110 0111

67.

8.

Find the Fourier transform of the half cosine pulse as shown below :

A.
 0.5 {sin c [0.25(f - 1)] + sin c [2.5(f + 1)]}
B.
 0.5 {sin c [0.5(f - 1)] + sin c [0.5(f + 1)]}
C.
 0.25 {sin c [0.25(f - 1)] + sin c [0.25 (f - 1)]}
D.
 0.25 {sin c [0.5(f - 1)] + sin c [0.5(f - 1)]}

Explanation:

The given signal can be expressed as multiplication of x1(t) and x2(t) as shown below.

where A = 2, T/2 = 0.25 => T = 0.5

x(t) = x1(t) x x2(t)

=> X(f) = X1(f) * X2(f)

Now X1(f) = [δ(f - f0) + δ(f + f0)]

= [sin c [T(f - f0)] + sin c[T(f + f0)]]

Now, A = 2, T = 0.5 and f0 = = 1

=> X(f) = 0.5[sin c (0.5(f - 1)) + sin c (0.5(f + 1))].

9.

In the signal flow graph of figure, y/x equals.

A.
 3
B.
 5/2
C.
 2
D.
 None of the above

Explanation:

P1 = 5 x 2 x 1 = 10

L1 = - 4

.

10.

A system with transfer function has an output for the input signal . Then, the system parameter 'p' is

A.
 3
B.
C.
 1
D.

Explanation:

|y(t)| = |M(ω)||x(t)|.

ω2 + p2 = ω2p2, 4 + p2 = 4p2

3p2 = 4, .

11.

The Taylor series expansion of at x = p is given by

A.
B.
C.
D.

Explanation:

.

12.

Consider the voltage transfer characteristic of a standard CMOS inverter

where region A corresponds to

A.
 NMOS and PMOS triode
B.
 Both are saturation
C.
 NMOS saturated PMOS linear
D.
 None of these

13.

Which one of the following is applicable to any network-linear or non-linear, active or passive, time-varying or invariant - as long as Kirchhoff laws are not violated?

A.
 Tellegen's theorem
B.
 Reciprocity theorem
C.
 Maximum power transfer theorem
D.
 Superposition theorem

14.

In a network with twelve circuit elements and five nodes, what is the minimum number of mesh equations?

A.
 24
B.
 12
C.
 10
D.
 8

15.

Assertion (A): The expression E = - ΔV, where E is the electric field and V is the potential is not valid for time varying fields.

Reason (R): The curl of a gradient is identically zero.

A.
 Both A and R are individually true and R is the correct explanation of A
B.
 Both A and R are individually true but R is not the correct explanation of A
C.
 A is true but R is false
D.
 A is false but R is true

16.

Which of the following are included in the architecture of a computer?

2. Instruction set, data formats
3. Secondary memory, operating system
Select the correct answer from the codes given below:

A.
 1 and 2
B.
 1 and 3
C.
 2 and 3
D.
 3 only

17.

Consider the following statements:
The klystron and travelling wave tube differ from each other,

1. In TWT the microwave circuit is non- resonant.
2. In klystron the microwave circuit is resonant.
3. TWT uses attenuator.
4. The wave is TWT is a non-propagating wave.
Which of the above statements are correct?

A.
 1 and 2 only
B.
 3 and 4 only
C.
 1, 2 and 3
D.
 2, 3 and 4

18.

Consider the function where F(s) is the Laplace transform of f(t). What is the steady-state value of f(t)?

A.
 Zero
B.
 One
C.
 Two
D.
 A value between - 1 and + 1

19.

A magnetic field in air is measured to be

What current distribution leads to this field?
[Hint: The algebra is trivial in cylindrical coordinates.]

A.
B.
C.
D.
 0

20.

Which of the following photodetector does not provide gain?

A.
 Phototransistor
B.
 Photoconductor
C.
 Avalanche photodiode
D.
 p-i-n photodiode