electrical

DC Motor MCQ Objective Questions and Answers Page - 2

1.

if the load current and flux of a dc motor are held constant and voltage applied across it  armature is increased by 54% , the speed of the motor will

Answer/ Hint      

Answer : A

Explanation :

2.

if the flux of a dc motor approaches zero,  its speed will

Answer/ Hint      

Answer : A

Explanation :

3.

A series motor is working drawing a load current of 1A from the line if now the load is reduced such that the current drawn is halved, the speed of the machine (neglecting the saturation and armatu

Answer/ Hint      

Answer : D

Explanation :

4.

A dc shunt motor runs at rated speed. If its field circuit gets open circuited, then soon after this the motor speed would tend to

Answer/ Hint      

Answer : C

Explanation :

5.

The speed of a dc shunt motor ____from no load to full load

Answer/ Hint      

Answer : A

Explanation :

6.

A dc shunt generator has an armature resistance of 0.1 and runs at 1200 rpm when delivering 50 kW at 250 V. The speed of the machine, when run as a motor fed from 250 V supply and drawing 50 kW wil

Answer/ Hint      

Answer : B

Explanation :

7.

The speed regulation of a dc motor is given as

Answer/ Hint      

Answer : C

Explanation :

8.

A dc motor having full load speed of 750 rpm and speed regulation of 10% will have no load speed of

Answer/ Hint      

Answer : A

Explanation :

9.

When  is the mechanical power developed by a dc motor maximum ?

Answer/ Hint      

Answer : C

Explanation :

10.

If the applied voltage to a dc machine is 230 V , then the back emf, for maximum power developed is

Answer/ Hint      

Answer : A

Explanation :

11.

The efficiency of a dc motor when developing maximum power will be about

Answer/ Hint      

Answer : C

Explanation :

12.

A dc motor develop the maximum mechanical power when the armature current is such that

Answer/ Hint      

Answer : B

Explanation :

13.

A 400 V shunt motor takes 5A at no load Ra=0.5 , Rf=200Ω what is the ratio of speed from full load to no load when the dc shunt mtoro takes 50 A on full load ?

Answer/ Hint      

Answer : A

Explanation :

14.

The dc motor, which can provides zero speed regulation at full load without any controller is

Answer/ Hint      

Answer : D

Explanation :

15.

A dc shunt motor having unsaturated magnetic circuit runs at 1,000rpm with rated voltage. If the applied voltage is half of the rated voltage, the motor  will run at

Answer/ Hint      

Answer : B

Explanation :

16.

What happens to the speed when the flux is reduced by 10% in a 200 V dc shunt motor having an armature resistance of 0.2 ohm carrying a current of 50 A and running at 960 rpm prior to weakening of<

Answer/ Hint      

Answer : B

Explanation :

17.

In a dc series motor, the torque developed in

Answer/ Hint      

Answer : C

Explanation :

18.

Torque developed by the armature of a dc motor is proportional to which one of the following

Answer/ Hint      

Answer : B

Explanation :

19.

A series motor drawing an armature current of  Ia is operating under saturated magnetic conditions The torque developed is the motor is proportional to

Answer/ Hint      

Answer : D

Explanation :

20.

What is the increase in torque expressed as percentage of initial torque, if the current drawn by a dc series motor is increased from 10A to 12A (neglect saturation )  ?

Answer/ Hint      

Answer : D

Explanation :

21.

ward Leonard control provides speed control

Answer/ Hint      

Answer : B

Explanation :

22.

For very sensitive and wide speed control, the preferable control methods is

Answer/ Hint      

Answer : D

Explanation :

23.

In Ward Leonard system, the lower limit of speed is imposed by

Answer/ Hint      

Answer : C

Explanation :

24.

In Ward Leonard method of speed control, the direction of rotation of the motor is reversed usually by reversing the connections of the

Answer/ Hint      

Answer : A

Explanation :

25.

The main disadvantages (s) of the Ward Leonard system is/ are

Answer/ Hint      

Answer : D

Explanation :

26.

For a given torque, reducing diverter resistance of a dc series motor

Answer/ Hint      

Answer : B

Explanation :

27.

A dc series motor is operating at rated speed with rated excitation it has two resistance R1 and R2 connected across the filed and the armature respectively. Speeds above the rated speed can be obt

Answer/ Hint      

Answer : C

Explanation :

28.

In series parallel control of dc series motor, the torque produced in series arrangement will be …………..of that in parallel arrangement

Answer/ Hint      

Answer : B

Explanation :

29.

The speed of a cumulatively compounded dc motor can be controlled by varying

Answer/ Hint      

Answer : D

Explanation :

30.

The function of the filed  regulator in a a dc compound motor is to

Answer/ Hint      

Answer : C

Explanation :

31.

A direct on line starter is used for starting motor

Answer/ Hint      

Answer : A

Explanation :

32.

If the speed of D.C shunt motor is increased the back e.m.f of the motor will

Answer/ Hint      

Answer : B

Explanation :

33.

What will happen if the back e.m.f of A D.C motor vanishes suddenly?

Answer/ Hint      

Answer : C

Explanation :

34.

In case of D.C shunt motors the speed is dependent on back e.mf only because

Answer/ Hint      

Answer : D

Explanation :

35.

In a D.c shunt motor, under the conditions of maximum power, the current in the armature will be

Answer/ Hint      

Answer : D

Explanation :

36.

Which DC motor will have least percentage increase of input current for the same percentage increase in the torque?

Answer/ Hint      

Answer : B

Explanation :

37.

These days D.C motors are widely used in

Answer/ Hint      

Answer : C

Explanation :

38.

By looking at which part of the motor, it can easily confirm that a particular motor is D.C motor?

Answer/ Hint      

Answer : C

Explanation :

39.

In which of the following applications D.C series motor is invariable tried?

Answer/ Hint      

Answer : A

Explanation :

40.

In D.C machines fractional pitch winding is used

Answer/ Hint      

Answer : D

Explanation :

41.

A three-point starter is considered suitable for

Answer/ Hint      

Answer : B

Explanation :

42.

Small D.C motors up to 5 H.P usually have

Answer/ Hint      

Answer : A

Explanation :

43.

In case the conditions for maximum power for a D.C motor are established, the efficiency of the motor will be

Answer/ Hint      

Answer : D

Explanation :

44.

A shearing machine has cyclic load consisting of intermittent light and hennery loads. Which of the following D.C motor will be suitable for5 this purpose?

Answer/ Hint      

Answer : C

Explanation :

45.

The ratio of starting torque to full load torque is least in case of

Answer/ Hint      

Answer : B

Explanation :

46.

In D.C motor which of the following can sustain the maximum temperature rise?

Answer/ Hint      

Answer : C

Explanation :

47.

Which of the following law/rule can be used to determine the direction of rotation of D.C motor?

Answer/ Hint      

Answer : D

Explanation :

48.

Which of the following load normally needs starting torque more than the rated torque?

Answer/ Hint      

Answer : B

Explanation :

49.

The starting resistance of a D.C motor is generally

Answer/ Hint      

Answer : A

Explanation :

50.

The speed of a D.C series motor is

Answer/ Hint      

Answer : D

Explanation :

<< Previous
DC Motor MCQ Objective Questions and Answers Page - 2
Next >>