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EEE :: D.C. Generators

  1. D.C. generator generally preferred for charging automobile batteries is

  2. A.

     Series generator

    B.

     Shunt generator

    C.

     Long shunt compound generator

    D.

     Any of the above

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  3. To avoid formation of grooves in the commutator of a D.C. machine

  4. A.

     The brushes of opposite polarity should track each other

    B.

     The brushes of same polarity should track each other

    C.

     Brush position has no effect on the commutator grooving

    D.

     All of the above

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  5. The main factor which leads to unstable parallel operation of flat and over compounded generators is

  6. A.

     their rising voltage characteristics

    B.

     unequal number of turns in their series field windings

    C.

     unequal speed regulation of their primemovers

    D.

     unequal series field resistances

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  7. The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except

  8. A.

     Armature reaction

    B.

     Armature resistance drop

    C.

     Field weakening due to armature reaction and armature

    D.

     Commutation

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  9. For a D.C. machines laboratory following type of D.C. supply will be suitable

  10. A.

     Rotary converter

    B.

     Mercury are rectifier

    C.

     Induction motor D.C. generator set

    D.

     Synchronous motor D.C. generator set

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  11. When two D.C. series generators are running in parallel, an equalizer bar is used

  12. A.

     To increase the speed and hence generated e.m.f.

    B.

     To increase the series flux

    C.

     So that two similar machines will pass approximately equal currents to the load

    D.

     To reduce the combined effect of armature reaction of both machines

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  13. When two D.C. generators are running in parallel an equalizer bar is used

  14. A.

     To increase the series flux

    B.

     To increase the generated e.m.f.

    C.

     To reduce the combined effect of armature reaction of both the machines

    D.

     So that the two identical machines will pass approximately equal currents to the load

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  15. The armature core of a D.C. generator is usually made of

  16. A.

     Silicon steel

    B.

     Copper

    C.

     Nonferrous material

    D.

     Cast-iron

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  17. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by

  18. A.

     Using conductor of annealed copper

    B.

     Using commutator with large number of segments

    C.

     Using carbon brushes of superior quality

    D.

     Using equalizer rings

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  19. Magnetic field in a D.C. generator is produced by

  20. A.

     Electromagnets

    B.

     Permanent magnets

    C.

     Both (A) and (B)

    D.

     None of the above

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