# SSC JE Electrical Important MCQ Part 6

SSC JE Electrical Important MCQ PDF Part 6

1.For domestic wiring, the most extensively used material is

A) Aluminium

B) Copper

C) Neither copper nor aluminium

D) Copper or aluminium

2.A substance that has a high retentiveness can be used for the manufacture of

A) Electromagnets

B) Paramagnets

C) Temporary magnets

D) Permanent magnets

3.For a slip ‘s’ and supply frequency ‘f’, the frequency of current in rotor will be

A) sf

B) f/s

C) f²/s

D) (1-s)f

4.The synchronous speed of a three phase induction motor having 20 poles and connected to a 50 Hz source is

A) 1200 RPM

B) 600 RPM

C) 300 RPM

D) 1000 RPM

5.The ballistic galvanometer is designed to deflect its needle proportional to ________ passing through its moving coil.

A) Heat energy

B) Magnetic force

C) Pressure energy

D) Charge

Answer  : D (The ballistic galvanometer is designed to deflect its indicating needle (or mirror) in a way that is proportional to the total charge passing through its moving coil or to a voltage pulse of short duration)

6.Which of the following semiconductor devices can be used for controlling the speed of a DC motor

A) Thyratron

B) Thermistor

C) Transistor

D) Thyristor

7.Equipment earthing is necessary to give protection against

B) The danger of electric shocks

C) Voltage fluctuation

D) The high temperature of the conductors

8.In a transmission system, a feeder feeds power to

A) Power plant substation

B) Generating substations

C) Service mains

D) Distributors

Answer  : B (Feeder transmits power from Generating station or substation to the distribution points)

9.An alternator has 20 poles and running at 300 RPM will generate alternating voltage and current whose frequency is

A) 100 Hz

B) 50 Hz

C) 30 Hz

D) 40 Hz

10.When a voltmeter-ammeter method is applied for the measurement of resistance, the voltmeter reads a value of 8.28 V and the ammeter reading is 4.14 mA, then the value of the resistance will be

A) 20 kΩ

B) 2 kΩ

C) 200 kΩ

D) 2 MΩ

Answer  : B (R=V/I=8.28 V/ 4.14 mA=2 kΩ)

11.The fusing factor of protective devices for medium level load is

A) 1.45

B) 2.38

C) 3.45

D) 0.95

Answer  : B (Fusing factor =minimum fusing current / current rating of fusing element. Fusing factor value is more than 1.The fusing factor of protective devices for medium level load is 1.45)

12.The difference between the synchronous speed and the actual speed of an induction motor is known as

A) Backlash

B) Lag

C) Slip

D) Regulation

13.Where is the control grid placed in a triode

A) Very near to cathode

B) Very near to plate

C) Very near to anode

D) Midway between plate and cathode

14.Relative permeability of a substance is less than the permeability of free space is known as

A) Paramagnetic

B) Non magnetic

C) Diamagnetic

D) Ferromagnetic

Answer  : C (A diamagnetic material has a constant relative permeability slightly less than 1.The permeability of free space (a vacuum ) is a physical constant equal to approximately 1.257 x 10 6 henry per meter)

15.If a power of 100 W is being supplied across a potential difference of 200 V, find the current flowing through the circuit.

A) 0.5 A

B) 1 A

C) 20 A

D) 2 A

16.Electricity produced from _______ is called piezoelectricity.

A) Heat

B) Pressure

C) Light

D) Velocity

Answer  : B (Piezoelectricity means the electricity which is produced due to the application of pressure)

17.If the load impedance in three phases are not equal to the load then it is said to be

A) Unbalanced supply

C) Balanced supply

18.Susceptibilities of diamagnetic material is

A) Unity

B) Zero

C) Negative

D) Positive

Answer  : B (Diamagnetic substances have negative susceptibilities (χ < 0); paramagnetic, superparamagnetic, and ferromagnetic substances have positive susceptibilities (χ > 0))

19.Which of the following wirings is suitable for lighting in low voltage installations

A) Surface conduit wiring

B) Concealed conduit wiring

C) TRS wiring

D) Casing wiring

20.Which of the following are the disadvantages of synchronous motors

A) Usually operate with higher efficiencies

B) Requires DC excitation

C) Ability to control the power factor

D) Electro-magnetic power varies linearly with the voltage