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EEE :: D.C. Generators

  1. The field coils of D.C. generator are usually made of

  2. A.

     Mica

    B.

     Copper

    C.

     Cast iron

    D.

     Carbon

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  3. A cumulatively compounded long shunt generator when operating as a motor would be

  4. A.

     Cumulatively compounded long shunt

    B.

     Differentially compounded long shunt

    C.

     Cumulatively compounded short shunt

    D.

     Differentially compounded short shunt

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  5. If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be

  6. A.

     Demagnetization only

    B.

     Cross magnetization as well as magnetization

    C.

     Cross-magnetization as well as demagnetizing

    D.

     Cross magnetization only

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  7. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be

  8. A.

     270 V

    B.

     267.5 V

    C.

     265 V

    D.

     257.4 V

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  9. Which of the following generators will be preferred if they are required to be run in parallel?

  10. A.

     Shunt generators

    B.

     Series generators

    C.

     Compound generators

    D.

     None of the above

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  11. In a D.C. generator the critical resistance can be increased by

  12. A.

     Increasing its field resistance

    B.

     Decreasing its field resistance

    C.

     Increasing its speed

    D.

     Decreasing its speed

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  13. In a D.C. machine, short-circuited field coil will result in

  14. A.

     odour of barning insulation

    B.

     unbalanced magnetic pull producing vibrations

    C.

     reduction of generated voltage for which excitation has to be increased to maintain the voltage

    D.

     all above

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  15. Eddy currents are induced in the pole shoes of a D.C. machine due to

  16. A.

     Oscillating magnetic field

    B.

     Pulsating magnetic flux

    C.

     Relative rotation between field and armature

    D.

     All above

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  17. Welding generator will have

  18. A.

     Lap winding

    B.

     Wave winding

    C.

     Delta winding

    D.

     Duplex wave winding

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  19. The demagnetizing component of armature reaction in a D.C. generator

  20. A.

     Reduces generator e.m.f.

    B.

     Increases armature speed

    C.

     Reduces interpoles flux density

    D.

     Results in sparking trouble

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