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 :

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