SSC JE Electrical Important MCQ Part 9

SSC JE Electrical Important MCQ PDF Part 9

1.Which of the following are the types of earthing system

A) Wire earthing

B) All of these

C) Pipe earthing

D) Plate earthing

2.Alternator is used to generate

A) Both AC and DC

B) DC

C) Light energy

D) AC

3.Working voltage of medium grade cables is

A) 500 V

B) 650 V

C) 100 V

D) 400 V

4.Mho relay is suitable for __________ transmission lines

A) Low voltage

B) Ultra High voltage

C) Both Ultra and extra high voltage

D) Extra-high voltage

5.The base of BJT is

A) Heavily doped

B) Moderately doped

C) Not doped

D) Lightly doped

Answer  : D (The base region of a BJT transistor is very thin and is lightly doped with current carriers)

6.In an airblast circuit breaker, why is compressed air used

A) Closing the contacts

B) Cooling the circuit breaker

C) Quenching the arc

D) Opening the contacts

7.Filament in an incandescent lamp is made of

A) Copper wire

B) Nichrome wire

C) Fuse wire

D) Tungsten wire

8.A coil of 600 turns and of resistance of 20 Ω is wound uniformly over a steel ring of mean circumference 30 cm and cross sectional area 9 cm². If the relative permeability of the ring is 1600. Find the value of reluctance.

A) 1.657 x 10⁵ AT/Wb

B) 2.657 x 10⁵ AT/Wb

C) 3.657 x 10⁵ AT/Wb

D) 4.657 x 10⁵ AT/Wb

Answer  : A (Given l=30 cm=0.3 m,A=9 cm²=9×10⁻⁴ m²,μᵣ=1600,μₒ=4π×10⁻⁷ Reluctance S=l/μᵣμₒA=0.3/1600×4π×10⁻⁷×9×10⁻⁴=1.657 x 10⁵ AT/Wb)

9.The full form of ACSR is

A) All Copper Standard Reinforced

B) Aluminium Conductor Steel Reinforced

C) All Copper Steel Reinforced

D) Aluminium Copper Steel Reinforced

10.Leakage coefficient is denoted by

A) φ

B) Ω

C) μ

D) λ

Answer  : D (The ratio of the total flux produced to the useful flux set up in the air gap of the magnetic circuit is called a leakage coefficient or leakage factor. It is denoted by (λ).)

11.Power is transmitted over transmission lines on high voltage, because

A) Current is reduced

B) Efficiency is increased

C) Conductor cost is reduced

D) Both conductor cost is reduced and efficiency is increased

12.What is the primary function of a choke in a tube light circuit

A) Limit the starting current

B) Limit the current after starting

C) Heat up the filament

D) Induce high voltage

Answer  : D (The purpose of the choke is to provide a very high voltage initially between the filaments (across the two ends of the tube light))

13.What is the purpose of shading coil in a shaded pole motor

A) Reduce rotational losses

B) Produce rotating magnetic field

C) Reduce friction loss

D) Reduce rough commutation

14.A P-N-P-N diode

A) May be made of any semiconductor

B) Is always made of germanium

C) May be made of either silicon or germanium

D) Is always made of silicon

Answer  : D (The Shockley diode or PNPN diode is a four layer (P-N-P-N), two terminals (namely anode and cathode) semiconductor switching device.PNPN used silicon and phosphorus)

15.The rotor current frequency in a slip-ring induction motor depends on

A) Amount of slip

B) Inductive reactance

C) Rotor inductor

D) Rotor conductor

Answer  : A (Rotor frequency = s*f)

16.A magnetic pressure which sets up or tends to set up flux in a magnetic circuit is called

A) Magnetic field

B) Cross magnetisation

C) Demagnetisation

D) Magnetomotive force

17.During raceway wiring, which colour wire is always used for neutral connections

A) Red

B) White

C) Either green or white

D) Green

Answer  : B (Black, Red and Blue are used for hot wires and White is used as the neutral wire in a 120/208 V circuit/ raceway wiring. Brown, Orange and Yellow are used as hot wires and gray is used as the neutral wire in a 277/480 V. For grounding, regardless of the voltage, Green (or a bare wire) is used)

18.Ceiling rose is used to take supply for a/an

A) Portable equipment

B) Fluorescent lamp

C) Electric iron

D) Heater of 2000 W

Answer  : B (A ceiling rose is used to make a safe and efficient connection between the circuit wiring of an installation au electric load such as, fan, lamp, fluorescent tube etc).

19.The thyristor is turned off when the anode current falls below

A) Holding current

B) Latching current

C) Forward current

D) Breakover current

20.In India, what is the frequency of the AC power line voltage

A) 120 Hz

B) 60 Hz

C) 100 Hz

D) 50 Hz