# Online Electronics and Communication Engineering Test - Electronics and Communication Engineering Test - Random Loading Test...

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.

If Va = 10 ∠0, Vb = 10 ∠ -120° and Vc = 10 ∠ -240°, then Va2 and Va0 are

A.
 10 and 0 respectively B.
 0 and 10 respectively C.
 0 and 0 D.
 10 and 10 Explanation:

Since it is a balanced system of voltages, Va2 and Va0 must be zero.

2.

In figure, the switch is closed at t = 0 when current through inductor is 6 A, the rate of change of current through resistor is 6 A/s. The value of L is A.
 1 H B.
 2 H C.
 3 H D.
 4 H Explanation:

i = 18(1 - et/L) = 6; . Therefore, L = 2H.

3.

The correct relation between energy and charge is

A.
 Energy = voltage/charge B.
 Charge = Energy x voltage C.
 Energy = voltage (charge)0.5 D.
 Energy = voltage x charge Explanation:

Energy = V x I x t since I x t = Q, energy = voltage x charge.

4.

Assertion (A): Power is the rate at which energy is supplied.

Reason (R): Energy = VIt.

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

5.

Match the following:

List I List II
A.Line commutation1. B.Resonant commutation2. C.Complementary commutation3. D.Self commutation4. A.
 A-1, B-4, C-2, D-3 B.
 A-1, B-2, C-3, D-4 C.
 A-4, B-1, C-3, D-2 D.
 A-2, B-3, C-4, D-1 6.

Television transmission is by

A.
 ground waves B.
 sky waves C.
 space waves D.
 all of the above Explanation:

The reception of signals by space waves is governed by line of sight range limited to about 75 kms or so. For frequencies above 30 MHz (generally used for television) communication is through space waves.

7.

The storage capacity of audio CD is 540 Mb per side.

A.
 True B.
 False 8.

Nyquist stability criterion uses open loop frequency response characteristics.

A.
 True B.
 False 9.

The probability density function (PDF) of a random variable X is as shown below The corresponding cumulative distribution function (CDF) has the form

A.  B.  C.  D.  Explanation:

Cumulative distribution function (Pdf) dx

Then when we integrate the line from (-1, 0) to (0, 1) we get a parabolic curve.

The maximum value of Pdf can be 1.

10.

The circuit shown in figure will A.
 oscillate at 456 kHz B.
 oscillate at 228 kHz C.
 oscillate at microwave frequency D.
 not oscillate 11.

Circuit shown in the figure is A.
 astable multivibrator B.
 monostable multivibrator C.
 VCO D.
 ramp Generator 12.

In figure, the function of resistor R is A.
 to reduce ripples in the output B.
 to improve voltage regulation C.
 to limit the surge current D.
 either (a) or (c) 13.

Which of these has 3 layers?

A.
 PIN diode B.
 Zener diode C.
 Schottky diode D.
 Photo diode Explanation:

p layer, i layer and n layer.

14.

A.
 silicon B.
 germanium C.
 diamond D.
 quartz 15.

Which of the following is a digital modulation technique?

A.
 PCM B.
 PSK C.
 DM D.
 All 16.

Which device uses Pneumatic fluid?

A.
 LED B.
 LCD C.
 VF display D.
 None of these 17.

Find RAB A.
 1 Ω B.  C.  D.
 2 Ω Explanation:

By solving    18.

In computers the size of secondary memory is usually much larger than that of primary memory.

A.
 True B.
 False 19.

The following statements are true with respect to "Cascode Amplifier".

1. The reduction in h12 and Miller capacitance result in negligible reverse internal feedback.
2. A's is large loads cannot be connected.
3. As a narrow band amplifier, it provides small range of cμ is reduced.
4. As a narrow band amplifier it provides small range of frequencies parameters the effect of cμ reduces.

A.
 only 1 B.
 only 1 and 4 C.
 only 2 and 4 D.
 only 1 and 3 Explanation:

Cascode is a wide band amplifier and it provides wide range of frequencies than CE stage and as is large, large loads can be connected.

20.

The system of linear equations 4x + 2y = 1 , 2x + y = 6 has

A.
 a unique solution B.
 no solution C.
 an infinite number of solutions D.
 exactly two distinct solutions Explanation:

4x + 1y = 7 → (1)

2x + y = 6 → (2)

(1) can be written as 2x + y = 3.5 → (3)

Now LHS of equations (2) and (3) are same but RHS is different which is not possible. Hence no solution.