Explore topic-wise MCQs in Electrical Machines.

This section includes 23 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

Power factor of a synchronous motor varies when the ___________

A. applied voltage is varied
B. load is changed
C. supply frequency and field excitation is changed
D. all of the mentioned
Answer» B. load is changed
Discussion
2.

The reactive power output of a synchronous generator is limited by ___________

A. armature current and field current
B. field current and load angle
C. load angle and prime mover input
D. armature current and prime mover input
Answer» B. field current and load angle
Discussion
3.

A synchronous machine is operating at constant load and at unity power factor. If its excitation is increased, then it operates as ___________

A. generator at lagging p.f
B. motor at lagging p.f
C. absorber of reactive power
D. generator at leading p.f
Answer» B. motor at lagging p.f
Discussion
4.

A synchronous machine is operating at constant load and at unity power factor. If its excitation is increased and then it operates as ___________

A. motor at leading p.f
B. motor at lagging p.f
C. absorber of reactive power
D. generator at leading p.f
Answer» B. motor at lagging p.f
Discussion
5.

A 3-phase, 400V, synchronous motor is providing load at 0.8 p.f. lagging. If the field current of the motor is continuously increased, then the _____________

A. power factor increases and then decreases
B. power factor is not affected
C. power factor decreases upto a certain value of field current and then increases
D. power facor increases simply
Answer» B. power factor is not affected
Discussion
6.

In a 3-phase cylindrical-rotor alternator, synchronous reactance is sum of mutual and leakage reactance.

A. True
B. False
Answer» C.
Discussion
7.

Consider the following statements and mark appropriately.

A. I is true
B. II is true
C. I and II are true
D. None of them are trueView Answer
Answer» D. None of them are trueView Answer
Discussion
8.

These days alternators are designed to have larger air gaps for __________

A. stable parallel operation
B. higher stability limit
C. sinusoidal mmf distribution
D. all of the mentioned
Answer» B. higher stability limit
Discussion
9.

A synchronous machine with its field winding on rotor and polyphase armature winding on stator. At steady state running condition, its air gap field is?

A. IV
B. I, II, IV
C. II, IV
D. IView Answer
Answer» B. I, II, IV
Discussion
10.

A synchronous machine with its field winding on stator and polyphase armature winding on rotor. At steady state, which of the following is not true for its air gap field?

A. stationary w.r.t. stator
B. rotating at double the speed Ns w.r.t. rotor
C. rotating in direction opposite to rotor
D. rotating at Ns w.r.t. rotor
Answer» E.
Discussion
11.

Auxiliary method of starting is not possib1e due to the fact that ____________

A. it can not be started under load
B. it can be only started under load
C. it is less efficient
D. all of the mentioned
Answer» B. it can be only started under load
Discussion
12.

Which method is/are used to perform magnetic locking?

A. I, II, III
B. II, III
C. II, I
D. IIView Answer
Answer» B. II, III
Discussion
13.

Synchronous motors are ___________

A. not self starting
B. self starting
C. single excited
D. none of the mentioned
Answer» B. self starting
Discussion
14.

A 3-phase, 400V, synchronous motor is providing load at 0.8 p.f. lagging. If the field current of the motor is continuously increased, then$

A. power factor increases and then decreases.
B. power factor is not affected
C. power factor decreases upto a certain value of field current and then increases.
D. power facor increases simply
Answer» B. power factor is not affected
Discussion
15.

In_a_3-phase_cylindrical-rotor_alternator,_synchronous_reactance_is_sum_of_mutual_and_leakage_reactance.$

A. True
B. False
Answer» C.
Discussion
16.

Power factor of a synchronous motor varies when

A. applied voltage is varied
B. load is changed
C. supply frequency and field excitation is changed
D. all of the mentioned
Answer» B. load is changed
Discussion
17.

The reactive power output of a synchronous generator is limited by

A. armature current and field current
B. field current and load angle
C. load angle and prime mover input
D. armature current and prime mover input
Answer» B. field current and load angle
Discussion
18.

A synchronous machine is operating at constant load and at unity power factor. If its excitation is increased, then it operates as

A. generator at lagging p.f
B. motor at lagging p.f
C. absorber of reactive power
D. generator at leading p.f
Answer» B. motor at lagging p.f
Discussion
19.

A_synchronous_machine_is_operating_at_constant_load_and_at_unity_power_factor.

A.
B. motor at leading p.f
C. motor at lagging p.f
Answer» B. motor at leading p.f
Discussion
20.

These days alternators are designed to have larger air gaps fo?

A. stable parallel operation
B. higher stability limit
C. sinusoidal mmf distribution
D. all of the mentioned
Answer» B. higher stability limit
Discussion
21.

Rating of the dc motor to be used in the starting of SM, should be higher than the synchronous motor.

A. True
B. False
Answer» C.
Discussion
22.

Auxiliary method of starting is not possib1e due to the fact that

A. it can not be started under load
B. it can be only started under load
C. it is less efficient
D. all of the mentioned
Answer» B. it can be only started under load
Discussion
23.

Synchronous motors are

A. not self starting
B. self starting
C. single excited
D. none of the mentioned
Answer» B. self starting
Discussion