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EEE :: D.C. Generators

  1. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be

  2. A.

     Zero

    B.

     Small

    C.

     The same as rated voltage

    D.

     High


  3. In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralized by all of the following except

  4. A.

     Interpoles

    B.

     Dummy coils

    C.

     Compensating winding

    D.

     Shifting of axis of brushes


  5. The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage

  6. A.

     Will be less than 250 V

    B.

     Will always be 250 V

    C.

     May be greater or less than 250 V

    D.

     None of the above


  7. While applying Fleming's right-hand rule to and the direction of induced e.m.f., the thumb points towards

  8. A.

     Direction of induced e.m.f.

    B.

     Direction of flux

    C.

     Direction of motion of the conductor if forefinger points in the direction of generated e.m.f.

    D.

     Direction of motion of conductor, if forefinger points along the lines of flux


  9. In a D.C. generator the critical resistance refers to the resistance of

  10. A.

     Brushes

    B.

     Field

    C.

     Armature

    D.

     Load


  11. As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately

  12. A.

     40 percent

    B.

     25 percent

    C.

     10 percent

    D.

     5 percent


  13. An exciter for a turbo generator is a

  14. A.

     Separately excited generator

    B.

     Shunt generator

    C.

     Series generator

    D.

     Compound generator


  15. In D.C. generators the polarity of the interpoles

  16. A.

     Is the same as that of the main pole ahead

    B.

     Is the same as that of the immediately preceding pole

    C.

     Is opposite to that of the main pole ahead

    D.

     Is neutral as these poles do not play part in generating e.m.f.


  17. Inter-pole flux should be sufficient to

  18. A.

     Neutralize the commutating self induced e.m.f.

    B.

     Neutralize the armature reaction flux

    C.

     Neutralize both the armature reaction flux as well as commutating e.m.f. induced in the coil

    D.

     Perform none of the above functions


  19. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is

  20. A.

     2

    B.

     4

    C.

     6

    D.

     8