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EEE :: Transformers

  1. The purpose of providing an iron core in a transformer is to

  2. A.

     provide support to windings

    B.

     reduce hysteresis loss

    C.

     decrease the reluctance of the magnetic path

    D.

     reduce eddy current losses

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  3. A good voltage regulation of a transformer means

  4. A.

     output voltage fluctuation from no load to full load is least

    B.

     output voltage fluctuation with power factor is least

    C.

     difference between primary and secondary voltage is least

    D.

     difference between primary and secondary voltage is maximum

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  5. If the percentage impedances of the two transformers working in parallel are different, then

  6. A.

     transformers will be overheated

    B.

     power factors of both the transformers will be same

    C.

     parallel operation will be not possible

    D.

     parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load

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  7. An ideal transformer will have maximum efficiency at a load such that

  8. A.

     copper loss = iron loss

    B.

     copper loss < iron loss

    C.

     copper loss > iron loss

    D.

     none of the above

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  9. A Buchholz relay can be installed on

  10. A.

     auto-transformers

    B.

     air-cooled transformers

    C.

     welding transformers

    D.

     oil cooled transformers

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  11. The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be

  12. A.

     6400 W

    B.

     1600 W

    C.

     800 W

    D.

     400 W

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  13. The size of a transformer core will depend on

  14. A.

     frequency

    B.

     area of the core

    C.

     flux density of the core material

    D.

     (A) and (B) both

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  15. A transformer cannot raise or lower the voltage of a D.C. supply because

  16. A.

     There is no need to change the D.C. voltage

    B.

     A D.C. circuit has more losses

    C.

     Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero

    D.

     None of the above

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  17. Which of the following loss in a transformer is zero even at full load ?

  18. A.

     Core loss

    B.

     Friction loss

    C.

     Eddy current loss

    D.

     Hysteresis loss

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  19. Part of the transformer which is most subject to damage from overheating is

  20. A.

     iron core

    B.

     copper winding

    C.

     winding insulation

    D.

     frame or case

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