Guru Academy and Labs Ch6: Electro Magnetic Induction MCQ Online Test

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12th PHYSICS

Exam Time : 01:30:00 Hrs 25 x 1 = 25 marks

Choose the wrong statement: *

1 point

( a ) When ever the amount of magnetic flux linked with a circuit changes, an e.m.f. is induced in the circuit.

( b ) The induced e.m.f. lasts so long as the change in magnetic flux continues

( c ) Large the amount of magnetic flux linked with a circuit, greater is the e.m.f. induced in it

( d ) The direction of induced e.m.f. is given by Lenz's Llaw.

When number of turns of a soleniod is doubled, its self inductance becomes k times, where k= *

1 point

( a ) 2

( b ) 1

( c ) 8

( d ) 4

The mutual inductance M of coil 1 with respect to coil 2 *

1 point

( a ) increases when they are brought nearer

( b ) depends on the current passing through the coils

( c ) increases when one of them is rotated about an axis

( d ) is the same as M of coil 2 with respect to coil 1

A metal plate is getting heated. It can be because *

1 point

( a ) a direct current is passing through the plate

( b ) it is placed in a time varying magnetic field

( c ) it is placed in a space varying magnetic field, but does not vary with time

( d ) a current is passing through the plate

The self inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increase as *

1 point

( a ) l and A increase

( b ) l decrease and A increase

( c ) l increase and A decrease

( d ) both l and A decrease

Enter your Name: *

SI unit of magnetic flux is *

1 point

( a ) henry

( b ) weber

( c ) coulomb

( d ) volt

A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because *

1 point

( a ) the magentic field is constant

( b ) the magnetic field is in the same plane as the circular coil and it may or may not vary

( c ) the magnetic field has a perpendicular componet whose magnitude is decreasing suitably

( d ) there is a constant magnetic field in the perpendicular direction.

An e.m.f. is produced in a coil, which is not connected to an external voltage source. This can be due to *

1 point

( a ) the coil being in a time varying magnetic field

( b ) the coil moving in a time varying magnetic field

( c ) the coil moving in a constant magnetic field

( d ) the coil is stationary in external spatially varying magnetic field, which does not change with

. *

1 point

A transformer is an electric device used for *

1 point

( a ) producing direct current

( b ) producing alternating current

( c ) changing d.c. into a.c.

( d ) changing a.c. voltages

Out of the following, choose the wrong statement : *

1 point

( a ) A transformer cannot work on d.c.

( b ) A transformer cannot change the frequency of a.c.

( c ) A transformer can produce a.c. power

( d ) In a transformer, when a.c. voltage is raised n times, the alternating current reduces to 1/ntime.

. *

1 point

. *

1 point

. *

1 point

Which one is not an application of eddy currents? *

1 point

a ) Magnetic brakes

( b ) speedometers

( c ) Induction furnace

( d ) Transformers

. *

1 point

. *

1 point

In which of the following appliances, Fleming's right hand rule for direction of induced current is not applicable? *

1 point

( a ) a.c.generator

( b ) d.c.generator

( c ) induction motor

( d ) transformer

The cause of induced e.m.f. is *

1 point

( a ) magnetic flux

( b ) magnetic field

( c ) area

( d ) change in magnetic flux

The frequency of a.c. generated depends on *

1 point

( a ) speed of rotation of coil

( b ) amplitude of a.c

( c ) size of coil

( d ) all the above

. *

1 point

( a ) 10 J

( b ) 20 J

( c ) 30 J

( d ) 40 J

The split ring arrangement is used by *

1 point

( a ) a.c. generator

( b ) d.c generator

( c ) choke coil

( d ) transformer

. *

1 point

A 50Hz AC current of crest value 1A flows through the primary of a transformer. If the mutual inductance between the primary and secondary be 0.5 H, the crest voltage induced in the secondary is *

1 point

( a ) 75 V

( b ) 150 V

( c ) 100 V

( d ) none of these

. *

1 point

( a ) 1 V

( b ) 10 V

( c ) 5 V

( d ) 2 V

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