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EEE :: Magnetic Circuit

  1. While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit?

  2. A.

     E.M.F.

    B.

     Current

    C.

     Current density

    D.

     Conductivity


  3. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it

  4. A.

     Lowers their power efficiency

    B.

     Increases their cost of manufacture

    C.

     Leads to their increased weight

    D.

     Produces fringing


  5. The unit of magnetic flux is

  6. A.

     Henry

    B.

     Weber

    C.

     Ampere-turn/weber

    D.

     Ampere/metre


  7. Laminated cores, in electrical machines, are used to reduce

  8. A.

     Copper loss

    B.

     Eddy current loss

    C.

     Hysteresis loss

    D.

     All of the above


  9. Those materials are well suited for making permanent magnets which have ________ retentivity and ________ coercivity.

  10. A.

     Low, high

    B.

     High, high

    C.

     High, low

    D.

     Low, low


  11. Those magnetic materials are best suited for making armature and transformer cores which have ________permeability and _________hysteresis loss.

  12. A.

     High, high

    B.

     Low, high

    C.

     High, low

    D.

     Low, low


  13. The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is ___________Vs

  14. A.

     50

    B.

     20

    C.

     0.05

    D.

     500


  15. Relative permeability of vacuum is

  16. A.

     1

    B.

     1 H/m

    C.

     1/4JI

    D.

     4n × 10' H/m


  17. In a magnetic material hysteresis loss takes place primarily due to

  18. A.

     Rapid reversals of its magnetization

    B.

     Flux density lagging behind magnetizing force

    C.

     Molecular friction

    D.

     It high retentivity


  19. Permeability in a magnetic circuit corresponds to_________ in an electric circuit.

  20. A.

     Resistance

    B.

     Resistivity

    C.

     Conductivity

    D.

     Conductance