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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 

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