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EEE :: D.C. Motors

  1. Usually wide and sensitive speed control is desired in case of

  2. A.

     Centrifugal pumps

    B.

     Elevators

    C.

     Steel rolling mills

    D.

     Colliery winders


  3. Which one of the following is not the function of pole shoes in a D.C. machine?

  4. A.

     To reduce eddy current loss

    B.

     To support the field coils

    C.

     To spread out flux for better uniformity

    D.

     To reduce the reluctance of the magnetic path


  5. Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity?

  6. A.

     Swinburne's test

    B.

     Hopkinson's test

    C.

     Field test

    D.

     Brake test


  7. When the armature of a D.C. motor rotates, e.m.f. induced is

  8. A.

     Self-induced e.m.f.

    B.

     Mutually induced e.m.f.

    C.

     Back e.m.f.

    D.

     None of the above


  9. A three point starter is considered suitable for

  10. A.

     Shunt motors

    B.

     Shunt as well as compound motors

    C.

     Shunt, compound and series motors

    D.

     All D.C. motors


  11. Which of the following motor has the poorest speed regulation?

  12. A.

     Shunt motor

    B.

     Series motor

    C.

     Differential compound motor

    D.

     Cumulative compound motor


  13. Which of the following loss in a D.C. generator varies significantly with the load current?

  14. A.

     Field copper loss

    B.

     Windage loss

    C.

     Armature copper loss

    D.

     None of the above


  15. As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit

  16. A.

     A resistance is connected in series with armature

    B.

     A resistance is connected parallel to the armature

    C.

     Armature is temporarily open circuited

    D.

     A high value resistor is connected across the field winding


  17. In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be

  18. A.

     Almost negligible

    B.

     Rated full-load current

    C.

     Less than full-load current

    D.

     More than full-load current


  19. 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

  20. A.

     2.36%

    B.

     4.76%

    C.

     6.77%

    D.

     8.84%