MCQ in DC motor 1-20

1. If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking
(a) regenerative
(b) plugging✔
(c) dynamic braking
(d) none of the above

2. Which of the following motors one will choose to drive the rotary compressor ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) Universal motor
(d) Synchronous motor✔

3. If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will
(a) increase✔
(b) decrease
(c) remain same
(d) become zero

4. Why are the D.C. motors preferred for traction applications ?
(a) Torque and speed are inversely proportional to armature current
(b) Torque is proportional to armature current
(c) Torque is proportional to square root of armature current
(d) The speed is inversely proportional to the torque and the torque is proportional to square of armature current✔

5. Which of the following motors is usually used in house-hold refrigerators ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) Single phase induction motor (split phase start or induction run motor)✔
(d) Reluctance motor

6. Which of the following motors is most suitable for signalling devices and many kinds of timers ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) Induction motor
(d) Reluctance motor✔

7. Which motor should not be started on no-load ?
(a) Shunt motor
(b) Cumulatively compounded motor
(c) Differentially compounded motor.
(d)Series motor✔

8. Ward-Leonard control is basically a
(a) voltage control method✔
(b) field divertor method
(c) field control method
(d) armature resistance control method

9. For constant torque drive which speed control method is preferred ?
(a) Field control
(b) Armature voltage control✔
(c) Shunt armature control
(d) Mechanical loading system

10. In Ward-Leonard control the lower limit of speed is imposed by
(a) residual magnetism of the generator✔
(b) core losses of motor
(c) mechanical losses of motor and generator together
(d) all of the above

11. No-load speed of which of the following motor will be highest ?
(a) Shunt motor
(b) Series motor✔
(c) Cumulative compound motor
(d) Differentiate compound motor

12. The direction of rotation of a D.C. series motor can be changed by
(a) interchanging supply terminals
(b) interchanging field terminals✔
(c) either of (a) and (b) above
(d) None of the above

13. Which of the following application requires high starting torque ?
(a) Lathe machine
(b) Centrifugal pump
(c) Locomotive✔
(d) Air blower

14. If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ?
(a) Series motor✔
(b) Shunt motor
(c) Differentially compound motor
(d) Cumulative compound motor

15. Which D.C. motor will be preferred for machine tools ?
(a) Series motor
(b) Shunt motor✔
(c) Cumulative compound motor
(d) Differential compound motor

16. Differentially compound D.C. motors can find applications requiring
(a) high starting torque
(b) low starting torque✔
(c) variable speed
(d) frequent on-off cycles

17. Which D.C. motor is preferred for elevators ?
(a) Shunt motor
(b) Series motor
(c) Differential compound motor
(d) Cumulative compound motor✔

18. According to Fleming’s left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of
(a) current in the conductor aovtaat of conductor✔
(c) resultant force on conductor
(d) none of the above

19. If the field of a D.C. shunt motor gets opened while motor is running
(a) the speed of motor will be reduced %
(b) the armature current will reduce
(c) the motor will attain dangerously high speed 1✔
(d) the motor will continue to nuvat constant speed

20. Starters are used with D.C. motors because
(a) these motors have high starting torque
(b) these motors are not self-starting
(c) back e.m.f. of these motors is zero initially
(d) to restrict armature current as there is no back e.m.f. while starting✔