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EEE :: D.C. Motors

  1. The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator?

  2. A.

     Hysteresis loss

    B.

     Field copper loss

    C.

     Armature copper loss

    D.

     Eddy current loss


  3. Which of the following load normally needs starting torque more than the rated torque?

  4. A.

     Blowers

    B.

     Conveyors

    C.

     Air compressors

    D.

     Centrifugal pumps


  5. Which of the following motors is most suitable for signaling devices and many kinds of timers?

  6. A.

     D.C. shunt motor

    B.

     D.C. series motor

    C.

     Induction motor

    D.

     Reluctance motor


  7. D.C. shunt motors are used for driving

  8. A.

     Trains

    B.

     Cranes

    C.

     Hoists

    D.

     Machine tools


  9. The condition for maximum power in case of D.C. motor is

  10. A.

     Back e.m.f. = 2 × supply voltage

    B.

     Back e.m.f. = I × supply voltage

    C.

     Supply voltage =I × back e.m.f.

    D.

     Supply voltage = back e.m.f.


  11. Which of the following law/rule can he used to determine the direction of rotation of D.C. motor?

  12. A.

     Lenz

    B.

     Faraday

    C.

     Coulomb’s law

    D.

     Fleming


  13. The speed of a D.C. motor can be varied by varying

  14. A.

     Field current

    B.

     Applied voltage

    C.

     Resistance in series with armature

    D.

     Any of the above


  15. Following motor is used where high starting torque and wide speed range control is required.

  16. A.

     Single phase capacitor start

    B.

     Induction motor

    C.

     Synchronous motor

    D.

     D.C. motor


  17. The current drawn by the armature of D.C. motor is directly proportional to

  18. A.

     The torque required

    B.

     The speed of the motor

    C.

     The voltage across the terminals

    D.

     None of the above


  19. The speed of a D.C. shunt motor more than its full-load speed can be obtained by

  20. A.

     Decreasing the field current

    B.

     Increasing the field current

    C.

     Decreasing the armature current

    D.

     Increasing the armature current