# SSC JE Electrical Important MCQ Part 10

SSC JE Electrical Important MCQ PDF Part 10

1.If a three-phase motor operates with only two-phases, it is called single-phasing. It will ultimately make the motor _______.

A) To run with triple speed

B) To run efficiently

D) To burn out

Answer  : D (When a three phase motor looses one of the phase supply voltage then it is called Single Phasing. Single Phasing a case when any one phase out of the three phases fails.Since one of the phases is now disconnected, current through other two phases will increase to produce the desired torque. The motor will run but would not be able to drive rated load.If motor is operating at higher load near to the rated load,Motor may get burnt)

2.Two way switches are used in ____ wiring

A) Staircase

C) Conduit

D) Batten

3.Which of the following diodes operate(s) in reverse breakdown region

A) Both PN junction diode and zener diode

B) LED

C) PN junction diode

D) Zener diode

4.A cluster of charges with an electric dipole moment is often called

A) Electric dipoles

B) Polarization

C) Electric susceptibility

D) Eddy currents

5.Paramagnetic substances are

A) Weakly attracted by a magnet

B) The same as that of dia magnetic substances

C) Weakly repelled by a magnet

D) Produced by heating iron above the curie point

Answer  : A (These are metals that are weakly attracted to magnets. They include aluminum, gold, and copper)

6.A JFET is also called ________ device

A) Neither unipolar nor bipolar

B) Both unipolar and bipolar

C) Unipolar

D) Bipolar

Answer  : A (All FETs can be called UNIPOLAR devices because the charge carriers that carry the current through the device are all of the same type i.e. either holes or electrons, but not both)

7.Calculate the total DC resistance of a 100 metre roll of 2.5 mm² copper wire if the resistivity of copper at 20° C is 1.72 x 10⁻⁸ Ω metre.

A) 0.867 Ω

B) 0.713 Ω

C) 0.214 Ω

D) 0.688 Ω

Answer  : D  (Given resistivity of copper at 20oC is 1.72 x 10-8, coil length L = 100m, the cross-sectional area A= 2.5mm2  = 2.5 x 10-6 metres2,R=ρL/A So R=1.72 x 10⁻8×100/ 2.5 x 10⁻⁶=688 mΩ=0.668 Ω)

8.The property of the coil of generating induced EMF due to the changing flux linked with it is called

A) Reactance

B) Capacitance

C) Resistance

D) Inductance

9.What is the SI unit of electric charge

A) Volt (V)

B) Joule (J)

C) Coulomb (C)

D) Ampere (A)

10.What is the most common and important type of fuse used in domestic application

A) Liquid type fuse

B) Kit-Kat type fuse

C) HRC fuse

D) Cartridge fuse

Answer  : B (Rewirable or Kit – Kat Type Fuses are a type of Low Voltage (LV) Fuses. They are most commonly used in house wiring, small industries and other small current applications)

11.In P-type semiconductor, the majority carriers are

A) Valence electrons

B) Free electrons

C) Neutrons

D) Holes

12.Which of the following value of a complex current wave is equal to the square root of the sum of the square of the RMS value of the individual components

A) Average value

B) Mean value

C) RMS value

D) Peak value

Answer  : C (The rms value of complex current or voltage wave is equal to the square root of the sum of the squares of the rms value of its individual components)

13.Synchronous motor when used for power factor improvement should be

A) Operated at no load with under excitation

C) Connected along with capacitor bank

D) Operated at no load with over excitation

14.The armature current of a synchronous motor has large value for

A) High excitation

B) Medium excitation

C) Both low and high excitation

D) Low excitation

Answer  : C (The magnitude of armature current varies with excitation. The current has large value both for low and high values of excitation (though it is lagging for low excitation and leading for higher excitation))

15.The unit of current is

A) Hertz

B) Volt

C) Ampere

D) Coulomb

16.The centre tap transformer is used in

A. Quarter Wave Rectifier

B. Half Wave Rectifier

C. Full Wave Rectifier

D. Bridge Rectifier

17.The important advantage of FET over BJT is

A. Very High Input Resistance

B. Very Low Input Resistance

C. Very High Input Current

D. Zero input Resistance

18.What is the speed of an induction motor when slip is 100%

A. Zero

Answer  : A (s = (ns – nr) 100% / ns ,where s = slip ns = synchronous speed of magnetic field (rev/min, rpm),nr = shaft rotating speed (rev/min, rpm),When the rotor is not turning (nr=0) then slip is 100 %)

19.The speed of an induction motor will be same as synchronous speed when slip is

A. Infinite

B. Unity

C. Half

D. Zero

Answer  : D ((s = (ns – nr) 100% / ns,When ns = nr,Then s=0)

20.In which motor, stator and rotor fields rotate simultaneously

A. DC series motor

B. Universal motor

C. Slip ring induction motor

D. Synchronous motor