DC Motor MCQs

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

(a) more than the normal speed
(b) less than the normal speed
(c) normal speed

(d) zero

Show Answer

Answer. c

2. 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

Show Answer

Answer. b

3. Which D.C. motor will be preferred for machine tools?

(a) Series motor
(b) Shunt motor

(c) Cumulative compound motor
(d) Differential compound motor

Show Answer

Answer. b

4. 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

Show Answer

Answer. b

5. 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

Show Answer

Answer. d

6. 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

Show Answer

Answer. d

7. If a D.C. motor is to be selected for conveyors, which motor would be preferred?

(a) Series motor
(b) Shunt motor
(c) Differentially compound motor
(d) Cumulative compound motor

Show Answer

Answer. a

8. Which of the following application requires high starting torque?

(a) Lathe machine
(b) Centrifugal pump
(c) Locomotive
(d) Air blower

Show Answer

Answer. c

9. Which D.C. motor is preferred for elevators?

(a) Shunt motor
(b) Series motor
(c) Differential compound motor
(d) Cumulative compound motor

Show Answer

Answer. d

10. 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

Show Answer

Answer. c

11. 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

Show Answer

Answer. b

12. If a D.C. motor is connected across the A.C. supply it will

(a) run at normal speed
(b) not run
(c) run at a lower speed
(d) burn due to heat produced in the field winding by .eddy currents

Show Answer

Answer. d

13. A D.C. series motor is that which

(a) has its field winding consisting of thick wire and fewer turns
(b) has a poor torque
(c) can be started easily without load
(d) has almost constant speed

Show Answer

Answer. a

14. 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

Show Answer

Answer. a

 

15. 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

Show Answer

Answer. b