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EEE :: D.C. Motors

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

  2. A.

     Series motor

    B.

     Shunt motor

    C.

     Cumulative compound motor

    D.

     Differential compound motor


  3. The speed of a D.C. series motor is

  4. A.

     Proportional to the armature current

    B.

     Proportional to the square of the armature current

    C.

     Proportional to field current

    D.

     Inversely proportional to the armature current


  5. The plugging gives the

  6. A.

     Zero torque braking

    B.

     Smallest torque braking

    C.

     Highest torque braking

    D.

     None of the above


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

  8. A.

     More than the normal speed

    B.

     Loss than the normal speed

    C.

     Normal speed

    D.

     Zero


  9. Which of the following motors one will choose to drive the rotary compressor?

  10. A.

     D.C. shunt motor

    B.

     D.C. series motor

    C.

     Universal motor

    D.

     Synchronous motor


  11. In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will

  12. A.

     Remain unchanged

    B.

     Reduce to one-fourth value

    C.

     Increase four folds

    D.

     Be doubled


  13. Which of the following motors is usually used in household refrigerators?

  14. A.

     D.C. shunt motor

    B.

     D.C. series motor

    C.

     Single phase induction motor (split phase start or induction run motor)

    D.

     Reluctance motor


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

  16. A.

     Shunt motor

    B.

     Series motor

    C.

     Differential compound motor

    D.

     Cumulative compound motor


  17. During rheostatic braking of D.C. series motors

  18. A.

     Motor is run as a generator

    B.

     Motor is reversed in direction

    C.

     Motor is run at reduced speed

    D.

     None of these


  19. In a D.C. generator all of the following could be the effects of iron losses except

  20. A.

     Loss of efficiency

    B.

     Excessive heating of core

    C.

     Increase in terminal voltage

    D.

     Rise in temperature of ventilating air