EASY PSC | Kerala PSC 013/2023 - Sub Engineer (Electrical) Answer key

Question 1

Which of the following statements are TRUE about the resistance of a material?
(i) Resistance varies directly as its area of cross section
(ii) Resistance varies inversely as the length of the material
(iii) Resistance does not depend on the nature of the material
(iv) Resistance depends on the temperature of the material

A

Both (i) and (iv)

B

Both (ii) and (iii)

C

Both (i) and (ii)

D

(iv) only

Question 2

Which of the following is NOT a good conductor of electricity?

A

Acids

B

Sea water

C

Pure mineral oil

D

Gold

Question 3

The SI unit of Electrical Conductivity is:

A

Siemens per meter

B

Siemens per square meter

C

Ohm per meter

D

Ohm-meter

Question 4

Two wires A and B have the same cross section and are made of the same material. Resistance of A is 600 Ω and Resistance of B is 200Ω . The number of times of A is longer than B is:

A

3

B

2

C

0.33

D

6

Question 5

If two identical 4A, 2Ω Norton equivalent circuits are connected in parallel with like polarity to like, the combined Norton equivalent circuit is:

A

8A, 4Ω

B

0A, 1Ω

C

8A, 1Ω

D

4A, 4Ω

Question 6

The Superposition theorem is essentially based on the concept of:

A

Duality

B

Linearity

C

Reciprocity

D

Non-linearity

Question 7

One Kilowatt hour of electrical energy equals:

A

3600 Joules

B

735.5 Watts

C

4186 Joules

D

860 Kilo-calorie

Question 8

Two similar electric charges of 1 Coulomb each are placed 1 meter apart in air. Force of repulsion between them would be nearly:

A

1 N

B

9 × 10⁹ N

C

0 N

D

8.85 x 10⁻¹² N

Question 9

If a dielectric slab of thickness 6 mm and 5 εᵣ = is inserted between the plates of an air capacitor with plate separation of 8 mm, it’s capacitance is :

A

Increased

B

Decreased

C

Almost halved

D

Unaffected

Question 10

A capacitor that stores a charge of 0.2 Coulombs at 10 volts has a capacitance of:

A

2 Farad

B

0.02 Farad

C

50 Farad

D

10 Farad

Question 11

Permeability in a magnetic circuit corresponds to ———————— in an Electric Circuit.

A

Reluctivity

B

Resistivity

C

Conductivity

D

Susceptibility

Question 12

The lifting power of an electromagnet depends on:

A

Pole area of electromagnet

B

Magnetic flux density

C

Shape of electromagnet

D

Both A) and B)

Question 13

Which of the following instruments are equally accurate on dc as well as ac circuits?

A

Dynamometer wattmeter

B

Moving iron ammeter

C

Induction wattmeter

D

PMMC voltmeter

Question 14

Induction watt hour meters are free from:

A

Phase error

B

Creeping error

C

Temperature error

D

Frequency error

Question 15

The RMS value of a half wave rectified current is 5A, it’s value for full wave rectification would be:

A

10/2 A

B

10/√2 A

C

10/π A

D

20/π A

Question 16

The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20Ω . If the frequency is increased to 100 Hz reactance becomes:

A

40Ω

B

20Ω

C

10Ω

D

5Ω

Question 17

Which of the following is NOT considered a fixed cost while calculating the cost of electric power generation?

A

Salaries of high officials

B

Interest on capital cost

C

Repair and maintenance

D

Taxes and Insurance

Question 18

If power factor is unity, the reactive power is:

A

Unity

B

Equal to I² R

C

Zero

D

A negative quantity

Question 19

In a series RLC circuit, R = 100 Ω, X_L = 300 Ω, X_C = 200 Ω . The phase angle of the circuit is:

A

0°

B

45°

C

180°

D

90°

Question 20

In an ac circuit, the ratio of KW/KVA represents:

A

Power factor

B

Peak factor

C

Load factor

D

Demand factor

Question 21

Speed/time curve for electric trains for city service does not have:

A

Coasting period

B

Free running period

C

Constant acceleration period

D

Braking period

Question 22

While considering train movement crest speed is the:

A

Maximum speed attained by a train during the run

B

Average speed attained by a train during the run

C

Ratio of distance between the stops and actual time of run

D

Ratio of distance between the stops and sum of actual time of run and stop time

Question 23

Magnetic materials are heated with the help of:

A

Radiation

B

Electric Arc

C

By Convection

D

Hysteresis loss

Question 24

During regenerative braking of electric motors:

A

It’s field is disconnected from the supply

B

It’s armature is reverse connected

C

It’s field is reverse connected

D

They are made to run as generators

Question 25

The advantage of corona effect in transmission line is that:

A

It works as a safety valve for electrical surges

B

It generates ozone

C

The overall efficiency of the transmission line is increased

D

Makes line current non sinusoidal

Question 26

The sag of transmission line is least affected by:

A

Temperature

B

Weight of the conductor per unit length

C

Length of the conductor

D

Current passes through the conductor

Question 27

An interconnector between two generating stations facilitates to:

A

Keep their voltages constant

B

Run them in parallel

C

Transfer of power in one particular direction only

D

Reduce losses in the transmission line

Question 28

The string efficiency of a suspension type insulator can be increased by:

A

By using longer cross arms

B

Providing guard ring

C

Using identical insulator discs

D

Both A) and B)

Question 29

Volume of copper required for an ac transmission line is inversely proportional to:

A

Line current

B

Length of line conductor

C

Transmitted power

D

Power factor

Question 30

Sheaths are used in underground cables to:

A

Provide insulation to the conductor

B

Protects from moisture and gases

C

Provide mechanical strength

D

All of the above

Question 31

Which of the following expressions depicts the diversity factor?

A

Ratio of maximum demand on the power station to the rated capacity of the power station

B

Ratio of maximum demand on the power station to its connected load

C

Ratio of sum of individual maximum demands to the maximum demand on the power station

D

Ratio of average load in the power station to the maximum demand during a given period

Question 32

Which of the following is NOT a Non Conventional energy source?

A

Magneto hydro dynamics generator

B

Natural gas

C

Fuel cell

D

Bio mass

Question 33

Which of the following methods is an electrical storage method of solar energy?

A

Inductor storage

B

Thermo-Chemical storage

C

Pebble bed storage

D

Flywheel storage

Question 34

Impedance relay is used for the protection of:

A

Medium transmission lines

B

Short transmission lines

C

Long transmission lines

D

Any of the above

Question 35

On which of the following effects of electric current, a fuse operates?

A

Photovoltaic effect

B

Electrostatic effect

C

Heating effect

D

Magnetic effect

Question 36

Which of the following circuit breakers are most suitable for the voltage 765 KV?

A

Vacuum circuit breakers

B

Air blast circuit breakers

C

SF6 circuit breakers

D

Air break circuit breakers

Question 37

Deflection torque in a measuring instrument:

A

Opposes control torque

B

Opposes damping torque

C

Both A) and B)

D

None of the above

Question 38

Due to phase error energy meter will read:

A

Active power

B

Reactive power

C

Power factor

D

None of the above

Question 39

The scale of a ammeter is uniform. Its type is:

A

Moving iron

B

Permanent magnet moving coil

C

Induction type

D

Dynamometer type

Question 40

Which of the following bridge is used for the measurement of dielectric loss?

A

Maxwell’s bridge

B

Anderson bridge

C

Schering bridge

D

De Sautty’s bridge

Question 41

In two – wattmeter method of power measurement, one of the wattmeter shows negative reading when the load power factor angle is:

A

0°

B

45°

C

Greater than 60°

D

60°

Question 42

The current passing through a 10Ω resistance is given by I = 4 + 2√2sin314t A. This current is measured by Permanent magnet moving coil meter is:

A

4A

B

6A

C

2√2A

D

√20 A

Question 43

Voltages V₁ = 5sinωt and V₂ = 10sinωt are connected to X and Y terminals of a CRO respectively. What is the shape of figure seen on the CRO?

A

A Circle

B

An Ellipse

C

A Parabola

D

A Straight Line

Question 44

In a digital voltmeter, the oscillator frequency is 500 KHz. The ramp voltage falls from 8V to V in 25ms. What is the number of pulses counted by the counter?

A

20

B

12500

C

5000

D

2500

Question 45

Hall effect transducers are used for measuring:

A

Current

B

Electric field

C

Magnetic field

D

Pressure

Question 46

As per the recommendation of ISI the number of outlets are permitted in a power circuit:

A

10 points

B

5 points

C

2 points

D

1 point

Question 47

The SI unit of Luminance is:

A

Candela

B

Lux

C

Candela/m²

D

Lumen

Question 48

A source of light of 1000 Candelas is situated 5 m above a working surface. Calculate the illuminance directly below the source in Lux:

A

25

B

200

C

500

D

40

Question 49

A fluorescent tube can be operated on:

A

AC only

B

DC only

C

Both AC as well as DC

D

None

Question 50

In which type of wiring vulcanized Indian rubber and polyvinyl chloride insulated wires are used as conductor?

A

CTS wiring

B

Cleat wiring

C

Lead sheathed wiring

D

Conduit wiring

Question 51

The loop earth wire shall be of size less than:

A

8 SWG

B

10 SWG

C

20 SWG

D

14 SWG

Question 52

What is the maximum length of the flexible conduit in the motor installation?

A

Less than 1.25 m

B

Less than 3 m

C

Less than 3.5 m

D

Maximum upto 5 m

Question 53

The Armature resistance of a 4-Pole Wave wound DC machine is 0.08Ω . If the armature is rewound as Lap winding. What is the armature resistance?

A

0.32Ω

B

0.16Ω

C

0.04Ω

D

0.02Ω

Question 54

In three point starter, the overload release coil operate, if ———————— current increases beyond set limit.

A

Field

B

Armature

C

Line

D

Neutral

Question 55

What is the shape of armature flux in DC machine due to armature reaction?

A

Flat topped

B

Saddle

C

Peaky

D

Triangular

Question 56

A DC series motor is running at rated speed. If the field winding is short circuited then the motor will

A

Stop

B

Run at dangerously high speed

C

Damage

D

All of the above

Question 57

A transformer is a

A

Constant flux device

B

Phase shifting device

C

Negative feedback circuit

D

All of the above

Question 58

Which winding structure require more insulation?

A

Concentric winding

B

Interleaved winding

C

Sandwiched winding

D

All of the above

Question 59

If the load power factor of transformer is 0.85 lagging, then its primary power factor is:

A

0.8 lag

B

0.95 lag

C

0.85 lag

D

Unity pf

Question 60

The ratio error of a current transformer mainly depends on:

A

Types of transformer used on secondary

B

Eddy current loss of the core

C

Power factor of the load

D

All of the above

Question 61

Skewing of squirrel cage rotor bars does not eliminate:

A

Space harmonics

B

Cogging

C

Magnetic hum

D

Crawling

Question 62

Slip ring induction motor has ———————— excitation current and ———————— full load power factor as compared to squirrel cage induction motor.

A

High, High

B

High, Low

C

Low, High

D

Low, Low

Question 63

The supply voltage to a induction motor is 192V instead of 240V. Determine reduction in starting current in percentage:

A

40%

B

50%

C

10%

D

20%

Question 64

Two identical alternators each are rated for 25 MVA, 11 KV having a sub transient reactance of 10% are connected in parallel. The short circuit level at the bus bar is:

A

500 MVA

B

400 MVA

C

125 MVA

D

100 MVA

Question 65

In a synchronous generator ratio of short circuit current to open circuit voltage is:

A

Synchronous reactance

B

Synchronous impedance

C

Synchronous admittance

D

Synchronous resistance

Question 66

A Synchronous motor is said to be over excited when it is operated at ———————— power factor.

A

Unity

B

Leading

C

Lagging

D

Leading or Lagging

Question 67

Reluctance motor is basically:

A

DC shunt motor

B

DC series motor

C

Single phase induction motor

D

Single phase synchronous motor

Question 68

The step angle of the stepper motor is 5° . If the stepping frequency is 3600 pulses per second, then the shaft speed will be:

A

50 rps

B

144 rps

C

2.5 rps

D

25 rps

Question 69

When a UJT is used for triggering an SCR, the wave shape of the voltage obtained from the UJT circuit is a:

A

Square wave

B

Sine wave

C

Trapezoidal wave

D

Saw-tooth wave

Question 70

TRIAC is a:

A

2 terminal bilateral switch

B

2 terminal switch

C

3 terminal bi-directional switch

D

3 terminal unilateral switch

Question 71

Choose the correct statement:

A

MOSFET is a uncontrolled device

B

MOSFET is a current controlled device

C

MOSFET is a voltage controlled device

D

MOSFET is a temperature controlled device

Question 72

An SCR is turned off by:

A

Reducing gate voltage to zero

B

Reducing anode voltage to zero

C

Reverse biasing the gate

D

None of the above

Question 73

The load voltage of a chopper can be controlled by varying the :

A

Firing angle

B

Extinction angle

C

Reactor position

D

Duty cycle

Question 74

Which of the device converts the AC supply of one frequency into an AC supply of a different frequency?

A

Pulse converter

B

Controller

C

Cycloconverter

D

Inverter

Question 75

The SMPS working is based on:

A

Chopper principle

B

Integral control principle

C

Frequency control principle

D

Phase control principle

Question 76

One of the basic requirements of servo motor is that it must produce high torque at all:

A

Loads

B

Speeds

C

Frequencies

D

Voltages

Question 77

Register of microprocessor which keeps track of the execution of program and which contain the memory address of next instruction to be executed is called:

A

Index register

B

Program counter

C

Memory address register

D

Instruction register

Question 78

What is the size of RAM and ROM in 8051 microcontroller?

A

128 byte RAM and 4 byte ROM

B

128 kB RAM and 4 kB ROM

C

128 byte RAM and 4 kB ROM

D

128 kB RAM and 4 byte ROM

Question 79

Which of the timer can operate in the 16 bit condition?

A

Timer 0

B

Timer 1

C

Timer 2

D

All of the above

Question 80

The programmable logic controller is classified into:

A

Two

B

Three

C

Four

D

Five

Question 81

Which of the following are the components of process automation?

A

Sensors

B

Controllers

C

Actuators

D

All of the above

Question 82

Distributed control system is ———————— system.

A

Computerized control

B

Component control

C

Compromise control

D

None of the above

Question 83

Which of the following is a correct statement?

A

PI controllers improves steady state response

B

PD controllers improves transient response

C

Both A) and B)

D

None of the above

Question 84

How many levels are present in Distributed Control System manufacturing?

A

3

B

4

C

5

D

6

Question 85

The band gap of Silicon at room temperature is:

A

1.4 eV

B

0.7 eV

C

1.1 eV

D

1.3 eV

Question 86

The emitter of a transistor is generally heavily doped because it:

A

Must possess low resistance

B

Is the first region of the transistor

C

Has to supply the charge carriers

D

Has to dissipate maximum power

Question 87

Ripple frequency of the output wave form of a full-wave rectifier when fed with a 50 Hz sine wave is:

A

25 Hz

B

200 Hz

C

50 Hz

D

100 Hz

Question 88

A zener diode, when used in voltage stabilization circuits, it is biased in:

A

Reverse breakdown region

B

Reverse bias region below the breakdown voltage

C

Forward bias region

D

Forward bias constant current mode

Question 89

Regulator IC 7905 provides regulated output voltage equal to:

A

18 V

B

– 12 V

C

9 V

D

– 5 V

Question 90

A network that shifts a waveform to a different DC level, without changing the appearance of the applied signal:

A

Voltage divider

B

Clamper

C

Clipper

D

Rectifier

Question 91

Which of the following multivibrator is called the flip-flop?

A

Astable multivibrator

B

Monostable multivibrator

C

Bistable multivibrator

D

Both B) and C)

Question 92

Following circuit is ———————— clipper.

A

Shunt negative

B

Shunt positive

C

Series negative

D

Series positive

Question 93

Two amplifiers are connected in series (cascaded). The first amplifier has a voltage gain of 12 and the second has a voltage gain of 15. Find the output ac signal if the input signal is 0.05 volt:

A

180 V

B

1.8 V

C

9 V

D

90 V

Question 94

How many types of coupling methods are there in a single stage transistor amplifier?

A

Three

B

Two

C

Four

D

One

Question 95

Consider the following statements:
1. A schmitt trigger circuit can be emitter-coupled-bi-stable circuit.
2. Schmitt trigger circuit exhibits hysteresis phenomenon.
3. The output of a Schmitt trigger will be triangular if the input is square wave.
Which of these statements are correct?

A

1, 2 and 3

B

2 and 3 only

C

1 and 2 only

D

1 and 3 only

Question 96

Op-Amp performs which type of mathematical operations?

A

Frequency dependent

B

Linear

C

Non-linear

D

All of the above

Question 97

What is the value is to be considered for a don’t care condition?

A

1

B

0

C

Any number except 0 and 1

D

Either 0 or 1

Question 98

In a J-K flip-flop, if J=K the resulting flip-flop is known as:

A

T flip-flop

B

D flip-flop

C

S-R flip-flop

D

S-K flip-flop

Question 99

Ripple counter also called:

A

VLSI counter

B

Synchronous counter

C

Asynchronous counter

D

SSI counter

Question 100

Based on how data is entered or shifted out, shift registers are classified into ——————— categories.

A

5

B

2

C

4

D

3