The previous years question paper for the examination conducted by DRDO for recruitment of Scientist is as follows:

A metal sphere with 1 m radius and a surface charge density of 10 Coulombs / m² is enclosed in a cube of 10m side. The total outward electric displacement normal to the surface of the cube is
40 Coulombs
10 Coulombs
5 Coulombs
None of the above.

The main reason for connecting a pulse transformer at the output stage of a thyristor triggering circuits to
Amplify the power of the triggering pulse.
Provide electrical isolation
Reduce the turn on time of the thyristor
Avoid spurious triggering of the thyristor due to nose.

A simple dc potentiometer is to be standardized by keeping the side wire setting at 1.0813 V. If by mistake, the setting is at 1.0138 V and the standardization is made to obtain a source voltage of 1.0318 V, then the reading of the potentiometer will be
1.0138 V
1.0183 V
(1.0138)² / 1.0183 V
(1.0138)² /V.

The maximum phase shift that can be obtained by using a lead compensator with transfer function
Gc (s) =
Is equal to:
Improve relative stability.
Increase the speed of response.
Increase bandwidth.
Increase overshoot.

Storage of 1 KB means the following number of bytes:
1000
964
1024
1064.


High intermediate frequency in a superheat receiver
Increases tracking problems.
Reduces adjacent channel rejection.
Improves selectivity.
None of the above.

In a 16-bit microprocessor, words are stored in two consecutive memory locations. The entire word can be read in one operations provided the first
Word is even.
Word is odd.
Memory location is odd.
Memory address is even.

Polythene is
A polymer of ethylene.
Vulcanized rubber.
Impregnated cotton.
Cellulose derivative.

Above the Curie temperature, the hysteresis loop of a ferroelectric material can be described by a
Inversely proportional to temperature and proportional to the square of the permanent dipole moment.
Proportional to temperature as well as to the square of the permanent dipole moment.
Proportional to temperature and inversely proportional to the square of the permanent dipole moment.
Inversely proportional to temperature as well as to the square of dipole moment.

A 3-phase step down transformer is connected to 6.6 KV mains and takes 10A. For which of the following connection the secondary line current will be least?
Delta – Delta
Star – Star
Delta – Star
Star – Delta.

In an induction motor, if the air gap is increased
Speed will reduce.
Efficiency will improve
Power factor will improve
Breakdown torque will reduce.

Which of the following are the features of a shaded pole motor?
Salient-pole stator.
Uniform air-gap
Tow stator windings one of which is a short-circuited ring.
Squirrel cage rotor.

Select the correct answer using the codes given below:
Codes:-
1 and 3
2 and 4
1, 3 and 4
1, 2 and 3

In a synchronous machine in case the axis of field flux is in line with the armature flux, then
The machine is working as synchronous motor.
The machine is working as synchronous generator.
The machine is said to be floating.
The machine will vibrate violently.

A cumulatively compound dc generator is supplying 20 a at 200 V. Now if the series field winding is short circuited, the terminal voltage will
Remain unaltered at 200 V
Rise to 220 V
Shoot up to a high value
Will reduce to 150 V.

An ACSR conductor having 7 steel strands and 24 aluminum conductor surrounding the steel strands is called
24 / 7 ACSR
7 / 24 ACSR
41 / 7 ACSR
7 / 31 ACSR

The current through a series RL circuit is when excited by a unit impulse voltage.
The values of R and L are respectively,
8,4
4,2
2,4
1,4

The critical frequency of an ionosphere layer is 10 MHz. What is the maximum launching angle from the horizon for which a 20 MHz wave will be reflected by the layer?
0°
30°
45°
90°