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electromagnetic induction MCQs

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

electromagnetic induction Mcqs
1. A small coil lies inside a large coil. The two coils are horizontal concentric and carry currents in opposite directions. The large coil will experience______________?
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A. No resultant force

B. A torque about horizontal axis

C. An upward force along the axis

D. A torque about vertical axis

2. Non inductive resistances are used in decreasing______________?
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A. Self inductance

B. Mutual inductance

C. Magnetic fields

D. Heating effect

3. An aeroplane of wingspan 10m flies from the equator towards the North Pole. The wings are perpendicular to the vertical component of the earths magnetic field (B = 410-5T). At maximum speed an emf of 96mV is induced across the wing tips. The maximum speed of the aeroplane is____________?
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A. 38.4msec-1

B. 200msec-1

C. 384msec-1

D. 150msec-1

4. The only difference between construction of D.C generator and A.C generator is that of_______________?
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A. commutator

B. coil

C. carbon brushes

D. magnetic field

5. A.C and D.C have the same______________?
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A. heating effect through a resistance

B. effect while passing through an inductance

C. effect in charging a capacitor

D. effect in charging a battery

6. A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance is_____________?
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A. 500 ohms

B. 50 ohms

C. 5000 ohms

D. 1000 ohms

7. If current in a conductor increases then according to Lenzs law self-induced voltage will____________?
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A. tend to decrease the amount of cur-rent

B. aid the applied voltage

C. produce current opposite to the in-creasing current

D. aid the increasing current

8. The out put voltage of a transformer is 3 times the input voltage then turns ratio will be________________?
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A. 1

B. 3

C. 3-Jan

D. 6

9. Which of the following is unit of inductance ?
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A. Webers/metre

B. Ampere turns

C. Ohm

D. Henry
10. A metal rod of 25 cm length is moving at a speed of 0.5/sec in direction perpendicular to 0.25T magnetic field. Emf produced in the rod is_____________?
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A. 0.03125 volt

B. 0 volt

C. 31.25 volt

D. 3.125 volt

11. A coil of wire is arranged with its plane perpendicular to a uniform magnetic field o flux density B. when the radius of the coil increases from r1 to r2 in time ?t then what is the emf induced in the coil ?
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A. ?B(r2-r1)2/?t

B. ?B/r22-r12/?t

C. ?B(r22+r12)/?t

D. ?B(r22-r12)/?t
12. The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as__________?
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A. capacitance

B. series aiding inductance

C. mutual inductance

D. self-inductance
13. Which circuit element(s) will oppose the change in circuit current ?
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A. Capacitance only

B. Inductance only

C. Resistance only

D. Inductance and capacitance

14. A.C cannot be used for________________?
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A. producing light

B. producing heat

C. magnetizing and electroplating

D. all the above

15. The core of a coil has a length of 200 mm. The inductance of coil is 6 mH. If the core length is doubled, all other quantities, remaining the same, the inductance will be_____________?
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A. 48mH

B. 24mH

C. 12 mH

D. 3 mH
16. Current produced by moving the loop of wire across a magnetic field is called_____________?
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A. mean square current

B. A.C current

C. D.C current

D. induced current
17. Which of the fpllowing inductor will have the least eddy current losses ?
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A. Powdered iron core

B. Laminated iron core

C. Iron core

D. Air core
18. Two 300 uH coils in series without mutual coupling have a total inductance of___________?
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A. 150 uH

B. 300 uH

C. 600 uH

D. 75 uH

19. Which one of the following devices does not function like an electric motor ?
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A. Voltmeter

B. Ammeter

C. Transformer

D. Galvanometer

20. The self-inductance of a solenoid is increased when a soft iron core is inserted into it. This is because the soft iron core_______________?
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A. Reduces the effect of eddy current

B. Increases the mutual inductance between the solenoid and the core

C. Improves the flux linkage between the turns of the coil

D. Decreases the resistance of the solenoid