electromagnetic induction MCQs – Page 2

Practise focused electromagnetic induction questions with marked answers for exam preparation and subject revision.

electromagnetic induction Mcqs

21. Magnetic compass needle will be deflecting if it is kept near________________?
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A. Accelerating charge

B. Soft iron

C. Static charge

D. Semi-conductor

22. Transformer works on the principle of________________?
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A. Law of conservation of power

B. Mutual induction

C. Lenzs law

D. Faradays law

23. When the motor is at its maximum speed then back emf will be______________?
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A. Zero

B. Maximum

C. No back emf

D. Intermediate values

24. Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla
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A. 1000 N

B. 600 N

C. 400 N

D. 100 N

25. A crack in the magnetic path of an inductor will result in________________?
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A. reduced inductance

B. zero inductance

C. increased inductance

D. unchanged inductance

26. In case of an inductance, current is proportional to___________?
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A. voltage across the inductance

B. magnetic field

C. both A. and B.

D. neither (A) nor (B)

27. The magnitude of the induced e.m.f. in a conductor depends on the______________?
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A. flux density of the magnetic field

B. amount of flux linkages

C. rate of change of flux-linkages

D. amount of flux cut

28. A dynamo converts______________?
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A. magnetic energy into mechanical energy

B. electrical energy into mechanical energy

C. magnetic energy into electrical energy

D. mechanical energy into electrical energy

29. Which of the following circuit element stores energy in the electromagnetic field ?
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A. Variable resistor

B. Inductance

C. Resistance

D. Condenser

30. 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
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A. Yes

B. No

31. A laminated iron core has reduced eddy-current losses because____________?
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A. the laminations are stacked vertfcally

B. the magnetic flux is concentrated in the air gap of the core

C. the laminations are insulated from each other

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

32. The direction of induced e.m.f. can be found by_____________?
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A. Flemings right hand rule

B. Laplaces law

C. Kirchhoff s voltage law

D. Lenzs law

33. Which of the following is not a unit of inductance ?
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A. Henry

B. Volt second per ampere

C. All of the above

D. Coulomb/volt ampere

34. Both the number of turns and the core length of an inductive coil are doubled. Its self-inductance will be_____________?
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A. unaffected

B. quadrupled

C. halved

D. doubled

35. The self inductances of two coils are 8 mH and 18 mH. If the co-efficients of coupling is 0.5, the mutual inductance of the coils is______________?
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A. 6 mH

B. 4 mH

C. 5 mH

D. 12 mH

36. The practical illustration of the phenomenon of mutual induction is____________?
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A. D.C dynamo

B. A.C generator

C. transformer

D. induction coil

37. An alternating current or voltage________________?
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A. varies in magnitude alone

B. changes its magnitude continuously and reverses its direction of flow after regularly recurring intervals.

C. fluctuates off and on

D. changes its direction again and again

38. The emf induced in a conductor of unit length moving with unit velocity at right angles to a magnetic field is equal to_____________?
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A. Motional emf

B. Magnetic flux density

C. Mutual induction

D. Torque

39. Power loss in actual transformer is due to_________________?
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A. Back emf

B. Eddy currents and magnetic hysterias

C. Small output

D. Soft iron core

40. Air-core coils are practically free from______________?
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A. hysteresis losses

B. eddy current losses

C. both (A) and (B)

D. none of the above

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