electrical

DC Motor MCQ Objective Questions and Answers Page - 4

1.

DC series motor is best suited for electric traction as

Answer/ Hint      

Answer : A

Explanation :

2.

A dc series motor is running at rated speed without any additional resistance in series. If an additional resistance is placed in series, ther speed mof motor

Answer/ Hint      

Answer : B

Explanation :

3.

A dc series motor is used for an overhauling load, it can work stably if

Answer/ Hint      

Answer : A

Explanation :

4.

A dc shunt motor is driving a constant torque load. On inserting an additional resistance in the armature circuit, the speed of the motor will

Answer/ Hint      

Answer : C

Explanation :

5.

A dc may have rising speed torque characteristic due to

Answer/ Hint      

Answer : C

Explanation :

6.

If the speed of a dc motor increase with load torque , then it is a

Answer/ Hint      

Answer : C

Explanation :

7.

A separately excited dc generator is feeding a dc shunt motor. If the load torque on the motor is halved approximately

Answer/ Hint      

Answer : A

Explanation :

8.

In a dc motor , if armature current is increased, keeping field current constant, the torque developed will

Answer/ Hint      

Answer : C

Explanation :

9.

If the supply voltage to a dc shunt motor is increased by 15% , which of the following will reduced ?

Answer/ Hint      

Answer : A

Explanation :

10.

A dc shunt motor is driving a constant torque load with normal excitation. If the filed current is halved then the motor will run at

Answer/ Hint      

Answer : D

Explanation :

11.

A dc shunt motor is driving a mechanical load at rated voltage with normal excitation. If the load torque is increased to double of the normal one, the speed of the motor will

Answer/ Hint      

Answer : D

Explanation :

12.

When a dc cumulative compound wound motor is loaded

Answer/ Hint      

Answer : A

Explanation :

13.

A belt driven cumulative compounded dc generator  is delivering power to the dc mains. If the belt snaps then the machine will run as a

Answer/ Hint      

Answer : B

Explanation :

14.

Flywheel is employed with a dc compound motor to reduce peak demand. The compound motor should be

Answer/ Hint      

Answer : C

Explanation :

15.

In a differentially compounded dc motor, if the shunt filed gets suddenly opened the motor will

Answer/ Hint      

Answer : A

Explanation :

16.

When the direction of power flow in a differentially compounded motor reverses, it will operate as a

Answer/ Hint      

Answer : A

Explanation :

17.

A differentially compounded dc motor with interpoles and with brushes on the neutral axis is to be driven as a generator in the same direction with the same polarity of the terminal voltage . It wi

Answer/ Hint      

Answer : B

Explanation :

18.

Running the machine at no load is inadvisable for

Answer/ Hint      

Answer : B

Explanation :

19.

The dc motor suitable for applications requiring high starting torque is

Answer/ Hint      

Answer : B

Explanation :

20.

The dc motor that drawn almost same power at different loads is

Answer/ Hint      

Answer : C

Explanation :

21.

A dc series motor is running with a divertor connected across in  field winding. If the divertor resistance is reduced then the speed of the motor will

Answer/ Hint      

Answer : B

Explanation :

22.

Two dc series motors are connected in series and are driving the same mechanical load. If the motors are now connected in parallel the speed will become

Answer/ Hint      

Answer : D

Explanation :

23.

In dc shunt motors , at start the filed excitation is kept at maximum value in order to

Answer/ Hint      

Answer : C

Explanation :

24.

A dc shunt motor has external resistance of Ra and Rf in the armature and filed circuits respectively Armature current at starting can be reduced by keeping

Answer/ Hint      

Answer : D

Explanation :

25.

Direct on line (DOL) starters are not suitable for starting large dc motors, because

Answer/ Hint      

Answer : A

Explanation :

26.

A DOL starter is employed fro starting motors of ratings up to

Answer/ Hint      

Answer : A

Explanation :

27.

In a dc shunt motor, the three point starter

Answer/ Hint      

Answer : D

Explanation :

28.

The dc motor starter handle should be moved

Answer/ Hint      

Answer : B

Explanation :

29.

A 4-point starter is used to start and control the speed of a

Answer/ Hint      

Answer : B

Explanation :

30.

The dynamic braking is generally used with ____dc motors

Answer/ Hint      

Answer : D

Explanation :

31.

Which D.C motor is generally preferred for cranes and hoists?

Answer/ Hint      

Answer : A

Explanation :

32.

Three-point starter can be used for

Answer/ Hint      

Answer : D

Explanation :

33.

Sparking is discouraged in a D.C motor because

Answer/ Hint      

Answer : B

Explanation :

34.

Speed control by Ward Leonard method gives uniform speed variation

Answer/ Hint      

Answer : B

Explanation :

35.

Flywheel is used with D.C compound motor to reduce the peak damaged by the motor, compound motor will have to be

Answer/ Hint      

Answer : C

Explanation :

36.

Following motor is used where high starting torque and wide speed range control is required

Answer/ Hint      

Answer : D

Explanation :

37.

In a differentially compounded D.C motor, if the shunt field suddenly opens

Answer/ Hint      

Answer : A

Explanation :

38.

Which of the following motor has the poorest speed regulation?

Answer/ Hint      

Answer : B

Explanation :

39.

Buses, trains. Trolleys, hoists, cranes require high starting torque and therefore make use of

Answer/ Hint      

Answer : A

Explanation :

40.

As the load is increased the speed of the D.C shunt motor will

Answer/ Hint      

Answer : A

Explanation :

41.

The armature torque of the D.C shunt motor is proportional to

Answer/ Hint      

Answer : B

Explanation :

42.

Which of the following method of speed control of D.C machine will offer minimum efficiency?

Answer/ Hint      

Answer : C

Explanation :

43.

Usually wide and sensitive speed control is desired in case of

Answer/ Hint      

Answer : D

Explanation :

44.

The speed of a motor falls from 1100 r.p.m at no-load at rated load. The speed regulation of the motor is

Answer/ Hint      

Answer : B

Explanation :

45.

The armature voltage control of D.C motor provides

Answer/ Hint      

Answer : A

Explanation :

46.

As there is no back e.m.f at the instant of starting a D.C motor, in order to prevent a heavy current from flowing through the armature circuit

Answer/ Hint      

Answer : A

Explanation :

47.

The speed of a D.C shunt motor can be increased by

Answer/ Hint      

Answer : B

Explanation :

48.

If Ia be the armature current, then speed of a D.C shunt motor is

Answer/ Hint      

Answer : A

Explanation :

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