Sparking at the commutator of a D.C. motor may result in____________?

Related Mcqs:

1. Sparking, is discouraged in a D.C. motor because_____________?

   A. it increases the input power con-sumption
   B. commutator gets damaged
   C. both A. and B.
   D. none of the above

2. 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

3. 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

4. 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

5. In the D.C. motor the iron losses occur in____________?

   A. the field
   B. the armature
   C. the brushes
   D. the commutator

6. 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

7. 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%

8. 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

9. 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

10. The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is______________?

    A. 2.36%
    B. 4.76%
    C. 6.77%
    D. 8.84%