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EEE :: Magnetic Circuit

  1. A ferrite core has less eddy current loss than an iron core because

  2. A.

     Ferrites have high resistance

    B.

     Ferrites are magnetic

    C.

     Ferrites have low permeability

    D.

     Ferrites have high hysteresis


  3. Conductance is analogous to

  4. A.

     Permeance

    B.

     Reluctance

    C.

     Flux

    D.

     Inductance


  5. Permanent magnets are normally made of

  6. A.

     Alnico alloys

    B.

     Aluminium

    C.

     Cast iron

    D.

     Wrought iron


  7. A material for good magnetic memory should have

  8. A.

     Low hysteresis loss

    B.

     High permeability

    C.

     Low retentivity

    D.

     High retentivity


  9. Reciprocal of reluctance is

  10. A.

     Reluctivity

    B.

     Permeance

    C.

     Permeability

    D.

     Susceptibility


  11. When both the inductance and resistance of a coil are doubled the value of

  12. A.

     Time constant remains unchanged

    B.

     Initial rate of rise of current is doubled

    C.

     Final steady current is doubled

    D.

     Time constant is halved


  13. Silicon steel is used in electrical machines because it has

  14. A.

     Low coercivity

    B.

     Low retentivity

    C.

     Low hysteresis loss

    D.

     High coercivity


  15. If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be

  16. A.

     Zero

    B.

     Small

    C.

     Large

    D.

     None of the above


  17. The unit of retentivity is

  18. A.

     Weber

    B.

     Weber/sq. m

    C.

     Ampere turn/meter

    D.

     Ampere turns


  19. An air gap is usually inserted in magnetic circuits to

  20. A.

     Increase m.m.f.

    B.

     Increase the flux

    C.

     Prevent saturation

    D.

     None of the above