DC Motor MCQ Question and Answer October 2, 2018October 3, 2018Ajay Sharma 1. The counter e.m.f. of a d.c. motor often exceeds the supply voltage aids the applied voltage helps in energy conversion regulates its armature voltage Continue >>2. The normal value of the armature resistance of a d.c. motor is 0.005 ohms 0.5 ohms 10 ohms 100 ohms Continue >>3. The mechanical power developed by the armature of a d.c. motor is equal to armature current multiplied by back e.m.f. power input minus losses power output multiplied by efficiency power output plus iron losses Continue >>4. The induced e.m.f. in the armature conductors of a d.c. motor is sinusoidal trapezoidal rectangular alternating Continue >>5. A d.c. motor can be looked upon as d.c. generator with the power flow reduced reversed increased modified Continue >>6. In a d.c. motor, the mechanical output power actually comes from field system air-gap flux back e.m.f. electrical input power Continue >>7. The maximum torque of d.c. motors is limited by commutation heating speed armature current Continue >>8. Which of the following quantity maintains the same direction whether a d.c. machine runs as a generator or as a motor ? induced e.m.f. armature current armature current supply current Continue >>9. Under constant load conditions, the speed of a d.c. motor is affected by field flux armature current back e.m.f. armature current and back e.m.f. Continue >>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. applied voltage torque Armature circuit resistance armature current Continue >>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. 20 240 5 220 Continue >>12. The shaft torque of a d.c. motor is less than its armature torque because of .......... losses. copper mechanical iron rotational. Continue >>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. 200 250 160 128 Continue >>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. 20 44 16.6 30.5 Continue >>15. If load on a d.c. shunt motor is increased, its speed is decreased due primarily to increase in its flux decrease in back e.m.f. increase in brush drop increase in armature current. Continue >>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 decrease by about 10 per cent remain unchanged increase by about 10 per cent increase by 20 per cent. Continue >>17. If the pole flux of a d.c. motor approaches zero, its speed will approach zero approach infinity no change due to corresponding change in back e.m.f. approach a stable value somewhere between zero and infinity. Continue >>18. If the field circuit of a loaded shunt motor is suddenly opened it would race to almost infinite speed it would draw abnormally high armature current circuit breaker or fuse will open the circuit before too much damage is done to the motor torque developed by the motor would be reduced to zero. Continue >>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 ? shunt series compound permanent magnet Continue >>20. A d.c. shunt motor is found suitable to drive fans because they require small torque at start up large torque at high speeds practically constant voltage small torque at start up and large torque at high speeds Continue >>21. As the load is increased, the speed of a d.c. shunt motor increases proportionately remains constant increases slightly reduces slightly Continue >>22. Between no-load and full-load, .......... motor develops the least torque series shunt cumulative compound differential compound Continue >>23. As compared to shunt and compound motors, series motor has the highest torque because of its comparatively .......... at the start. lower armature resistance stronger series field fewer series turns larger armature current Continue >>24. When load is removed, .......... motor will run at the highest speed. shunt cumulative-compound differential compound series Continue >>25. A series motor is best suited for driving lathes cranes and hoists shears and punches machine tools Continue >>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 54 N-m 81 N-m 108 N-m None of the above Continue >>27. The d.c. series motor should never be switched on at no load because the field current is zero The machine does not pick up The speed becomes dangerously high It will take too long to accelerate. Continue >>28. A shunt d.c. motor works on a.c. mains unsatisfactorily satisfactorily not at all none of the above Continue >>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. twice, half thrice, one third half, twice four times, one-fourth Continue >> DC Motor MCQ Question and AnswerResultShare your Results : Facebook Twitter Google+ VK PLAY AGAIN !Please share it, your one share can change my life.