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ECE :: Electromagnetic Induction

  1. A laminated iron core has reduced eddy-current losses because

  2. A.

     More wire can be used with less D.C. resistance in coil

    B.

     The laminations are insulated from each other

    C.

     The magnetic flux is concentrated in the air gap of the core

    D.

     The laminations are stacked vertically


  3. In case of an inductance, current is proportional to

  4. A.

     Voltage across the inductance

    B.

     Magnetic field

    C.

     Both A and B

    D.

     Neither A)nor B


  5. An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is

  6. A.

     20 Wb

    B.

     2 Wb

    C.

     0.2 Wb

    D.

     0.02 Wb


  7. The law that the induced e.m.f. and current always oppose the cause producing them is due to

  8. A.

     Faraday

    B.

     Lenz

    C.

     Newton

    D.

     Coulomb


  9. The magnitude of the induced e.m.f. in a conductor depends on the

  10. A.

     Flux density of the magnetic field

    B.

     Amount of flux cut

    C.

     Amount of flux linkages

    D.

     Rate of change of flux-linkages


  11. A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be nearly

  12. A.

     50 N

    B.

     120 N

    C.

     240 N

    D.

     480 N


  13. A crack in the magnetic path of an inductor will result in

  14. A.

     Unchanged inductance

    B.

     Increased inductance

    C.

     Zero inductance

    D.

     Reduced inductance


  15. Lenz's law is a consequence of the law of conservation of

  16. A.

     Induced current

    B.

     Charge

    C.

     Energy

    D.

     Induced e.m.f.