1000+ Electrical Machines Quiz, Top MCQs On Electrical Machines

April 29, 2021April 15, 2022 Darshan Vaniya

Hello guys, welcome back to my blog. In this article, I will share electrical machines quiz questions, top MCQ on electrical machines that is most commonly asked in many online tests, etc.

If you have any electrical, electronics, and computer science doubts, then ask questions. You can also catch me on Instagram – CS Electrical & Electronics And Chetan Shidling.

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Electrical Machines Quiz

1) If the speed of the D.C. shunt motor is increased, the back EMF of the machine will be____________.

a) Decrease
b) Increase
c) Not change
d) (a) and (b) both

Answer

2) For the same rating weight of D.C. machine will be_____________.

a) Same as A.C. machine
b) More than A.C. machine
c) Less than A.C. machine
d) None of above

Answer

3) The core of the transformer must have

a) Low reluctance
b) High resistance
c) High reluctance
d) Low resistance

Answer

4) A DC generator without a commutator is a

a) AC generator
b) DC motor
c) DC generator
d) Induction motor

Answer

5) Buchholz relay is provided on the transformer to

a) indicate minor faults inside the transformer
b) indicate minor & major faults and isolate the transformer during a major fault
c) isolate the transformer during a major fault
d) indicate major fault inside the transformers

Answer

6) Why HV winding is always placed above LV windings in core type transformers?

a) To reduce copper loss
b) Reduce insulation cost
c) To provide better cooling
d) To provide more mechanical strength

Answer

7) A synchronous motor is useful in industrial applications due to its property of______.

a) Improve power factor
b) Speed is constant
c) Can always be adjusted to operate at the unity power factor
d) All of these

Answer

8) What is common between induction generator and induction motor

a) Both required reactive power
b) Both can not run at synchronous speed
c) Both known as singly exciting machine
d) All of these

Answer

9) The effect of leakage flux in transformer is to__________.

a) Increase copper loss
b) Decrease copper loss
c) Cause voltage drop in windings
d) none of the above

Answer

10) Efficiency of PMSM is ____________.

a) 92% to 97%
b) 85% to 90%
c) 90% to 95%
d) None of the above

Answer

11) Maximum loss in D.C. machine is due to __________.

a) Eddy current
b) Hysteresis loss
c) Copper loss
d) Frictional loss

Answer

12) Which is the basic thing required to produce torque in any motor?

a) Stator flux
b) Rotor flux
c) (a) and (b) both
d) Interaction between stator and rotor flux

Answer

13) The tap changer in an electrical power transformer is provided on_____.

a) LV winding
b) HV winding
c) Both winding
d) Either LV or HV winding

Answer

14) The back emf in D.C. machine______.

a) Oppose the applied voltage
b) Aids the applied voltage
c) Aids the armature current
d) None of the above

Answer

15) Open circuit test is used to find_____.

a) Copper loss
b) Total equivalent resistance
c) Turns ratio
d) Leakage reactance

Answer

16) Which of the following connections is good for a 3-phase, 4-wire system?

a) Δ – Δ
b) Y – Y
c) Δ – Y
d) Y – Δ

Answer

17) Which of the following machine have maximum efficiency?

a) Power transformer
b) Power generator
c) DC motor
d) Induction motor

Answer

18) Armature reaction of an unsaturated DC machine is

a) Cross-magnetizing
b) Demagnetizing
c) Magnetizing
d) None of the above

Answer

19) The synchronous machine is also called a doubly excited machine, the reason for that is

a) It can be over-excited
b) Both rotor and stator are excited
c) It has two sets of rotor poles
d) All of these

Answer

20) What is the role of the starter in a 3-phase induction motor?

a) To limit heavy starting current
b) To provide overload and under-voltage protection
c) To avoid malfunctioning produce due to a large drop inline
d) All of these

Answer

21) Transformers are rated in kVA but not in kW because

a) Load power factor is often known
b) kVA is fixed whereas kW depends on load p.f
c) total transformer loss depends on volt-ampere
d) it has become customary

Answer

22) Where do we need to use a synchronous motor?

a) For constant speed operation
b) For we need to control the operating power factor
c) Where we have starting arrangement
d) All of these

Answer

23) Which generator is good for feeding long DC transmission lines?

a) Series generator
b) Shunt generator
c) Over compound generator
d) Flat compound generator

Answer

24) In an oil-filled transformer, the application of oil is for

a) Cooling
b) Insulation
c) Both cooling and insulation
d) Preventing the accumulation of dust

Answer

25) Which of the following motor can operate on both types of P.F.? (lagging as well as leading)

a) DC series motor
b) Wound rotor induction motor
c) Squirrel cage induction motor
d) Synchronous motor

Answer

26) The main purpose of providing tertiary winding in a 3-phase transformer

a) To suppress harmonic voltages and to limit voltages unbalance when the main load is asymmetrical
b) To interconnect three supply systems operated at different voltages
c) Both of these
d) None of these

Answer

27) The armature of the DC generator is laminated for