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ECE :: Electromagnetic Induction

  1. Current changing from 8 A to 12 A in one second induced 20 volts in a coil. The value of inductance is

  2. A.

     5 mH

    B.

     10 mH

    C.

     5 H

    D.

     10 H


  3. A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is

  4. A.

     3500 mH

    B.

     350 mH

    C.

     250 mH

    D.

     150 mH


  5. The direction of induced e.m.f. can be found by

  6. A.

     Laplace's law

    B.

     Lenz's law

    C.

     Fleming's right hand rule

    D.

     Kirchhoff s voltage law


  7. In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will

  8. A.

     Increase

    B.

     Decrease

    C.

     Remain the same

    D.

     Initially increase and then decrease


  9. Higher the self-inductance of a coil,

  10. A.

     Lesser its weber-turns

    B.

     Lower the e.m.f. induced

    C.

     Greater the flux produced by it

    D.

     Longer the delay in establishing steady current through it


  11. The inductance of a coil will increase under all the following conditions except

  12. A.

     When more length for the same number of turns is provided

    B.

     When the number of turns of the coil increase

    C.

     When more area for each turn is provided

    D.

     When permeability of the core increases


  13. The self-inductance of the coil may be defined as equal to the e.m.f. induced in volts when the current in the circuit changes at the rate of unit Weber turns.

  14. A.

     Yes

    B.

     No


  15. As per Faraday's laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it

  16. A.

     Lies perpendicular to the magnetic flux

    B.

     Lies in a magnetic field

    C.

     Cuts magnetic flux

    D.

     Moves parallel to the direction of the magnetic field


  17. The coefficient of coupling between two air core coils depends on

  18. A.

     Self-inductance of two coils only

    B.

     Mutual inductance between two coils only

    C.

     Mutual inductance and self inductance of two coils

    D.

     None of the above


  19. Air-core coils are practically free from

  20. A.

     Hysteresis losses

    B.

     Eddy current losses

    C.

     Both A and B

    D.

     None of the above