DC Motors MCQ Multiple Choice Questions Answers for Practice

Q: 1. The condition for maximum power in case of D.C. motor is

Correct Answer is: back e.m.f. = | x supply voltage

Q: 2. The current drawn by the armature of D.C. motor is directly proportional to

Correct Answer is: the torque required

Q: 3. The direction of rotation of a D.C. series motor can be changed by

Correct Answer is: interchanging field terminals

Q: 4. The hysteresis loss in a D.C. machine least depends on

Correct Answer is: Rate of flow of ventilating air

Q: 5. The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ?

Correct Answer is: armature copper loss

Q: 6. The main disadvantage of the Ward-Leonard control method is

Correct Answer is: all of the above

Q: 8. The plugging gives the

Correct Answer is: highest torque braking

Q: 9. The power mentioned on the name plate of an electric motor indicates

Correct Answer is: the output power available at the shaft

Q: 10. The purpose of retardation test on D.C. shunt machines is to find out

Correct Answer is: stray losses

Q: 11. The ratio of starting torque to full-load torque is least in case of

Correct Answer is: shunt motors

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

back e.m.f. = | x supply voltage
supply voltage = | x back e.m.f.
supply voltage = back e.m.f.
back e.m.f. = 2 x supply voltage

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

the speed of the motor
the voltage across the terminals
none of the above
the torque required

3. The direction of rotation of a D.C. series motor can be changed by

interchanging field terminals
either of a and b above
None of the above
interchanging supply terminals

4. The hysteresis loss in a D.C. machine least depends on

Maximum value of flux density
Volume and grade of iron
Rate of flow of ventilating air
Frequency of magnetic reversals

5. The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ?

field copper loss
armature copper loss
eddy current loss
hysteresis loss

6. The main disadvantage of the Ward-Leonard control method is

high maintenance cost
low efficiency at Hght loads
all of the above
high initial cost

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

8. The plugging gives the

smallest torque braking
highest torque braking
none of the above
zero torque braking

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

the power drawn in kVA
the gross power
the output power available at the shaft
the power drawn in kW

10. The purpose of retardation test on D.C. shunt machines is to find out

eddy current losses
field copper losses
windage losses
stray losses

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

shunt motors
compound motors
none of the above
series motors

12. The speed of a D.C. motor can be varied by varying

applied voltage
resistance in series with armature
any of the above
field current

13. The speed of a D.C. series motor is

proportional to the square of the armature current
proportional to field current
inversely proportional to the armature current
proportional to the armature current

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

increasing the resistance in field circuit
reducing the resistance in the field circuit
reducing the resistance in the armature circuit
increasing the resistance in armature circuit

15. The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by

decreasing the armature current
increasing the armature current
increasing the excitation current
reducing the field current

16. The speed of a D.C. shunt motor more than its full-load speed can be obtained by

increasing the field current
decreasing the armature current
increasing the armature current
decreasing the field current

17. The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is

4.76%
6.77%
8.84%
2.36%

18. The starting resistance of a D.C. motor is generally

around 500 Q
1000 Q
infinitely large
low

19. The total losses in a well designed D.C. generator of 10 kW will be nearly

500 W
1000 W
1500 W
100 W

20. The type of D.C. motor used for shears and punches is

series motor
differential compoutid D.C. motor
cumulative compound D.C. motor
shunt motor

21. These days D.C. motors are widely used in

air compressors
electric traction
machine shops
pumping sets

22. Three point starter can be used for

shunt motor only
compound motor only
both shunt and compound motor
series motor only

23. To get the speed of D.C, motor below the normal without wastage of electrical energy is used.

rheostatic control
any of the above method
none of the above method
Ward Leonard control

24. Torque developed by a D.C. motor depends upon

active length of the conductor
current flow through the conductors
all above factors
magnetic field

25. Usually wide and sensitive speed control is desired in case of

elevators
steel rolling mills
colliery winders
centrifugal pumps

26. Ward-Leonard control is basically a

field divertor method
field control method
armature resistance control method
voltage control method

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

The motor will continue to run
The armature may burn
The motor will run noisy
The motor will stop

28. When the armature of a D.C. motor rotates, e.m.f. induced is

mutually induced e.m.f.
back e.m.f.
none of the above
self-induced e.m.f.

29. When two D.C. series motors are connected in parallel, the resultant speed is

loss than the normal speed
normal speed
zero
more than the normal speed

30. Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversingand speed control

three point starter is used
four point starter is used
all above can be used
drum type controller is used

Dive into the world of DC Motors with our comprehensive collection of multiple-choice questions and answers. Whether you're a student studying electrical engineering, a technician working with motors, or simply intrigued by the principles of electromechanical systems, our meticulously curated selection covers a wide range of topics. Explore fundamental concepts such as motor types, operating principles, speed control methods, and practical applications in various industries. With our user-friendly interface and detailed explanations, mastering the intricacies of DC motors has never been more engaging and accessible. Start your journey towards understanding this essential component of electrical machinery today!