DC Motor MCQ Question and Answer

1. The counter e.m.f. of a d.c. motor

2. The normal value of the armature resistance of a d.c. motor is

3. The mechanical power developed by the armature of a d.c. motor is equal to

4. The induced e.m.f. in the armature conductors of a d.c. motor is

5. A d.c. motor can be looked upon as d.c. generator with the power flow

6. In a d.c. motor, the mechanical output power actually comes from

7. The maximum torque of d.c. motors is limited by

8. Which of the following quantity maintains the same direction whether a d.c. machine runs as a generator or as a motor ?

9. Under constant load conditions, the speed of a d.c. motor is affected by

10. It is possible to increase the field flux and, at the same time, increase the speed of a d.c. motor provided its .......... is held constant.

11. The current drawn by a 120 - V d.c. motor of armature resistance 0.5 Ω and back e.m.f. 110 V is .......... ampere.

12. The shaft torque of a d.c. motor is less than its armature torque because of .......... losses.

13. A d.c. motor develops a torque of 200 N-m at 25 rps. At 20 rps it will develop a torque of .......... N-m.

14. Neglecting saturation, if current taken by a series motor is increased from 10 A to 12 A, the percentage increase in its torque is ........ percent.

15. If load on a d.c. shunt motor is increased, its speed is decreased due primarily to

16. If the load current and flux of a d.c. motor are held constant and voltage applied across its armature is increased by 10 per cent, its speed will

17. If the pole flux of a d.c. motor approaches zero, its speed will

18. If the field circuit of a loaded shunt motor is suddenly opened

19. Which of the following d.c. motor would be suitable for drives requiring high starting torque but only fairly constant speed such as crushers ?

20. A d.c. shunt motor is found suitable to drive fans because they require

21. As the load is increased, the speed of a d.c. shunt motor

22. Between no-load and full-load, .......... motor develops the least torque

23. As compared to shunt and compound motors, series motor has the highest torque because of its comparatively .......... at the start.

24. When load is removed, .......... motor will run at the highest speed.

25. A series motor is best suited for driving

26. A 220 V shunt motor develops a torque of 54 N-m at armature current of 10 A. The torque produced when the armature current is 20 A, is

27. The d.c. series motor should never be switched on at no load because

28. A shunt d.c. motor works on a.c. mains

29. A 200 V, 10 A motor could be rewound for 100 V, 20 A by using .......... as many turns per coil of wire, having .......... the cross-sectional area.

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