D.C. Motors Multiple Choice Questions And Answers In English -02

1. 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
Ans: B

2. Which of the following application requires high starting torque ?
(A) Lathe machine
(B) Centrifugal pump
(C) Locomotive
(D) Air blower
Ans: C

3. 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
Ans: A

4. 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
Ans: B

5. For a D.C. shunt motor if the excitation is changed
(A) torque will remain constant
(B) torque will change but power will remain constant
(C) torque and power both will change
(D) torque, power and speed, all will change
Ans: B

6. Which motor has the poorest speed control?
(A) Differentially compounded motor
(B) Cumulatively compounded motor
(C) Shunt motor
(D) Series motor
Ans: D

7. Which D.C. motor will be preferred for machine tools ?
(A) Series motor
(B) Shunt motor
(C) Cumulative compound motor
(D) Differential compound motor
Ans: B

8. 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
Ans: B

9. Which D.C. motor is preferred for elevators ?
(A) Shunt motor
(B) Series motor
(C) Differential compound motor
(D) Cumulative compound motor
Ans: D

10. 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
Ans: A

11. 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
Ans: C

12. In D.C. shunt motors as load is reduced
(A) the speed will increase abruptly
(B) the speed will increase in proportion to reduction in load
(C) the speed will remain almost/constant
(D) the speed will reduce
Ans: C

13. For starting a D.C. motor a starter is required because
(A) it limits the speed of the motor
(B) it limits the starting current to a safe value
(C) it starts the motor
(D) none of the above
Ans: B

14. The type of D.C. motor used for shears and punches is
(A) shunt motor
(B) series motor
(C) differential compound D.C. motor
(D) cumulative compound D.C. motor
Ans: D

15. To get the speed of D.C, motor below the normal without wastage of electrical energy is used.
(A) Ward Leonard control
(B) rheostatic control
(C) any of the above method
(D) none of the above method
Ans: A

16. can be obtained by
(A) decreasing the field current
(B) increasing the field current
(C) decreasing the armature current
(D) increasing the armature current
Ans: A

17. A direct on line starter is used: for starting motors
(A) up to 5 H.P.
(B) up to 10 H.P.
(C) up to 15 H.P.
(D) up to 20 H.P.
Ans: A

18. In which of the following applications D.C. series motor is invariably tried?
(A) Starter for a car
(B) Drive for a water pump
(C) Fan motor
(D) Motor operation in A.C. or D.C.
Ans: A

19. A three point starter is considered suitable for
(A) shunt motors
(B) shunt as well as compound motors
(C) shunt, compound and series motors
(D) all D.C. motors
Ans: B

20. What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
(A) The motor will stop
(B) The motor will continue to run
(C) The armature may burn
(D) The motor will run noisy
Ans: C