electrical

DC Motor MCQ Objective Questions and Answers Page - 3

1.

In an electric motor , the electromagnetic torque developed is

Answer/ Hint      

Answer : A

Explanation :

2.

The torque speed characteristic of a dc shunt motor is

Answer/ Hint      

Answer : B

Explanation :

3.

The horse power obtained from the motor shaft is called the

Answer/ Hint      

Answer : B

Explanation :

4.

In a dc motor , the shaft torque is less than armature torque . This is due to

Answer/ Hint      

Answer : C

Explanation :

5.

The mechanical output available  at the dc motor shaft is equal to

Answer/ Hint      

Answer : D

Explanation :

6.

If Nis the speed of a dc series motor and Ia is the armature current then 

Answer/ Hint      

Answer : A

Explanation :

7.

For small values of armature current Ia, the torque developed by a dc series motor is proportional to

Answer/ Hint      

Answer : B

Explanation :

8.

For higher values of armature current Ia, the torque developed by a dc series motor is proportional to

Answer/ Hint      

Answer : A

Explanation :

9.

For higher value of armature current, the speed of a dc series motor is

Answer/ Hint      

Answer : D

Explanation :

10.

T and P are the developed electromagnetic torque and the shaft power of a dc series motor. If losses are neglected, then for constant terminal voltage

Answer/ Hint      

Answer : D

Explanation :

11.

In comparison to shunt and compound motors a dc series motor develops high torque at start. It is due to its comparatively

Answer/ Hint      

Answer : B

Explanation :

12.

A fly wheel is normally fitted to

Answer/ Hint      

Answer : C

Explanation :

13.

An electric motor with “constant output power ” will have a torque speed characteristic in the form of a

Answer/ Hint      

Answer : D

Explanation :

14.

T is the load torque of a dc series motor having linear magnetization and negligible armature resistance. Speed of the motor is

Answer/ Hint      

Answer : A

Explanation :

15.

An electric train employing a dc series motor is running at a fixed speed, when a sudden slight drop in the mains voltage occurs. This would result in

Answer/ Hint      

Answer : A

Explanation :

16.

In a dc series motor, if armature current is reduced to 70 % of its original value , the torque of the motor will be reduced by

Answer/ Hint      

Answer : B

Explanation :

17.

When the torque of a dc series motor is tripled the power approximately increases by

Answer/ Hint      

Answer : C

Explanation :

18.

When an electric train is moving down a hill, the dc motor will operate is a dc

Answer/ Hint      

Answer : B

Explanation :

19.

A dc series motor must not be started on no load because it would

Answer/ Hint      

Answer : C

Explanation :

20.

In case of a dc series motor it is possible to have finite no load speed if a resistance is connected across its

Answer/ Hint      

Answer : B

Explanation :

21.

If an additional resistance is connected in series with a dc series motor operating at rated speed of the motor will

Answer/ Hint      

Answer : A

Explanation :

22.

If a resistance is connected across the armature of a dc series motor , it speed for a constant load torque will

Answer/ Hint      

Answer : B

Explanation :

23.

Field diverter method of speed control of a dc series motor gives speeds above rated one due to reduction of

Answer/ Hint      

Answer : A

Explanation :

24.

The  field diverter resistance for a dc series motor is of the order of

Answer/ Hint      

Answer : A

Explanation :

25.

The current drawn by a dc motor at starting is

Answer/ Hint      

Answer : D

Explanation :

26.

High inrush of current during a starting of a dc motor can  efficiently be restricted to a safer value by increasing the ……..resistance

Answer/ Hint      

Answer : B

Explanation :

27.

The dc motor draws high current at the starting instant due to absence of back emf . In order to prevent this high inrush of current at start, a resistance is connected

Answer/ Hint      

Answer : C

Explanation :

28.

For efficient operation of a dc motor, the additional resistance inserted in he armature circuit should be

Answer/ Hint      

Answer : B

Explanation :

29.

Three point starters are not suitable for application where speed variation by flux control is required because the motor may

Answer/ Hint      

Answer : C

Explanation :

30.

If the no –voltage release in a dc motor starter fails to operate on failure of supply, on resumption of supply the motor will

Answer/ Hint      

Answer : D

Explanation :

31.

In a D.C series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to

Answer/ Hint      

Answer : C

Explanation :

32.

The current drawn by the armature of D.C motor is directly proportional to the

Answer/ Hint      

Answer : A

Explanation :

33.

The power mentioned on the name plate of an electric motor indicates

Answer/ Hint      

Answer : D

Explanation :

34.

In Ward Leonard method of speed control of a D.C motor, change in speed of the motor is obtained by the

Answer/ Hint      

Answer : A

Explanation :

35.

Which D.C motor has got maximum self-loading property?

Answer/ Hint      

Answer : D

Explanation :

36.

Which D.C motor will be suitable along with flywheel for intermittent light and heavy loads?

Answer/ Hint      

Answer : C

Explanation :

37.

If a D.C shunt motor is working at no load and if shunt field circuit suddenly opens

Answer/ Hint      

Answer : C

Explanation :

38.

D.C series motors are used

Answer/ Hint      

Answer : D

Explanation :

39.

For the same H.P rating and full load speed. Following motor has poor starting torque

Answer/ Hint      

Answer : C

Explanation :

40.

Sparking at the commutator of a D.C motor may result in

Answer/ Hint      

Answer : D

Explanation :

41.

Which of the following motor is preferred for operation in highly explosive atmosphere?

Answer/ Hint      

Answer : C

Explanation :

42.

If the supply voltage for a D.C motor is increased, which of the following will decrease?

Answer/ Hint      

Answer : C

Explanation :

43.

When the speed of a D.C motor increases

Answer/ Hint      

Answer : A

Explanation :

44.

As compared to an induction motor, the air gap in a D.C motor is

Answer/ Hint      

Answer : D

Explanation :

45.

Field winding of a D.C series motor is usually provided with track wire

Answer/ Hint      

Answer : C

Explanation :

46.

Which one of the following is not the function of pole shoes in a D.C machine?

Answer/ Hint      

Answer : A

Explanation :

47.

The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f to applied voltage is

Answer/ Hint      

Answer : D

Explanation :

48.

The condition for maximum power in case of D.C motor is

Answer/ Hint      

Answer : B

Explanation :

49.

For which of the following applications a D.C motor is preferred over an A.C motor?

Answer/ Hint      

Answer : C

Explanation :

50.

In D.C machines the residual magnetism is of the order of

Answer/ Hint      

Answer : A

Explanation :

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