What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?

Related Mcqs:

1. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________?

   A. nothing will happen to the motor
   B. this will make armature to take heavy current, possibly burning it
   C. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses D. motor will run at very slow speed

2. In a differentially compounded D.C. motor, if shunt field suddenly opens____________?

   A. the motor will first stop and then run in opposite direction as series motor
   B. the motor will work as series motor and run at slow speed in the same direction
   C. the motor will work as series motor and run at high speed in the same direction
   D. the motor will not work and come to stop

3. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________?

   A. this will make armature to take heavy current, possibly burning it
   B. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
   C. nothing will happen to motor
   D. motor will come to stop

4. By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

   A. Frame
   B. Shaft
   C. Commutator
   D. Stator

5. Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be_____________?

   A. level compounded
   B. under compounded
   C. cumulatively compounded
   D. differentially compounded

6. One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven_______________?

   A. runs as a generator
   B. does not run as a generator
   C. also runs as a motor comes to stop after sometime

7. 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

8. In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________?

   A. 100%
   B. around 90%
   C. anywhere between 75% and 90%
   D. less than 50%

9. In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to

   A. 100% of the previous value
   B. 50% of the previous value
   C. 25% of the previous value
   D. 10% of the previous value
   E. none of the above

10. For which of the following applications a D.C. motor is preferred over an A.C. motor ?

    A. Low speed operation
    B. High speed operation
    C. Variable speed operation
    D. Fixed speed operation