# Class 12th Physics – 7 Electromagnetic Induction MCQs

#### The polarity of induced EMF in a coil is such that it tends to produce a current which opposes the change in magnetic flux that produced it.

Correct! Wrong!

The polarity of induced EMF in a coil is such that it tends to produce a current which opposes the change in magnetic flux that produced it.

#### Moving charges produce

Correct! Wrong!

Moving charges produce magnetic field.

#### The induced electromotive force in a coil is

Correct! Wrong!

The induced electromotive force in a coil is equal to the negative time rate of change in magnetic flux.

#### If the north pole of a bar magnet is moved towards a coil, the magnetic pole induced on the face of the coil that is towards the north pole of the bar magnet is

Correct! Wrong!

According to Lenz’s law, the EMF induced in coil opposes the change that causes it. Hence, when the north pole of a bar magnet is moved towards the coil, the magnetic pole induced on the face of the coil that is towards the north pole of the bar magnet is the north pole.

#### If the south pole of a bar magnet is moved away from a coil, the magnetic pole induced on the face of the coil that is towards the south pole of the bar magnet is ____.

Correct! Wrong!

According to Lenz’s law, the EMF induced in coil opposes the change that causes it. Hence, when the south pole of a bar magnet is moved away from the coil, the magnetic pole induced on the face of the coil that is towards the south pole of the bar magnet is the north pole.

#### If the north pole of a bar magnet is moved away from a coil, the magnetic pole induced in the on the face of the coil that is towards the north pole of the bar magnet is ____.

Correct! Wrong!

According to Lenz’s law, the EMF induced in coil opposes the change that causes it. Hence, when the north pole of a bar magnet is moved away from the coil, the magnetic pole induced on the face of the coil that is towards the north pole of the bar magnet is the south pole.

#### The induced EMF due to the motion of a conductor in a magnetic field is called motional EMF.

Correct! Wrong!

The induced EMF due to the motion of a conductor in a magnetic field is called motional EMF.

#### Select the odd device among the given ones ____.

Correct! Wrong!

Electric motor works on the principle of magnetic effect of electric current, whereas bicycle dynamo, electric transformer and generator works on the principle of electromagnetic induction.

#### The motional EMF induced in a conductor increases with ____.

Correct! Wrong!

The motional EMF induced in a conductor increases with increase in the speed of the conductor.

#### There are two coils, one connected to a galvanometer and the other connected to a battery. The deflection of the needle in the galvanometer increases when: (i) A soft iron core is introduced in the coil connected to the battery (ii) The number of turns in the coil connected to the battery is increased

Correct! Wrong!

The deflection of the needle in the galvanometer increases when the magnetic flux associated with the coil connected to the galvanometer increases. This can be done either by introducing a soft iron core in the second coil or by increasing the number of turns in the second coil, which is connected to the battery or doing the both.

#### The relative motion between a magnet and a coil ____.

Correct! Wrong!

The relative motion between a magnet and a coil changes the magnetic flux associated with the coil.

#### (i) When a bar magnet is moved towards a coil, a repulsive force is experienced. (ii) The EMF induced in the coil opposes the cause that produces it.

Correct! Wrong!

When a bar magnet is moved towards a coil, a like pole is induced on the face towards the near end of the coil and hence a repulsive force is experienced. This is in accordance with Lenz’s law.

#### The phenomenon in which an electric current is generated by varying magnetic fields is called electromagnetic induction.

Correct! Wrong!

The phenomenon in which an electric current is generated by varying magnetic fields is called electromagnetic induction.

#### The magnetic flux ____.

Correct! Wrong!

Magnetic flux is the dot product of the area vector and the magnetic induction. Its magnitude does not change with direction and hence, it is always a scalar quantity.

#### There are two coils, one connected to a galvanometer and the other connected to a battery. The needle in the galvanometer deflects

Correct! Wrong!

The needle in the galvanometer of the first coil deflects when the two coils are moved relative to each other.

#### The change in magnetic flux with time linked with a coil: (i) Induces magnetic field in the coil (ii) Induces electric current in the coil

Correct! Wrong!

The change in magnetic flux linked with a coil induces electric current in the coil.

#### Whenever there is relative motion between a magnet and a coil, electric current is induced in the coil.

Correct! Wrong!

Whenever there is relative motion between a magnet and a coil, electric current is induced in the coil.

#### If the south pole of a bar magnet is moved towards a coil, the magnetic pole induced in the on the face of the coil that is towards the south pole of the bar magnet is

Correct! Wrong!

According to Lenz’s law, the EMF induced in coil opposes the change that causes it. Hence, when the south pole of a bar magnet is moved towards the coil, the magnetic pole induced on the face of the coil that is towards the south pole of the bar magnet is the south pole.

#### The galvanometer connected to a closed coil shows deflection ____.

Correct! Wrong!

The galvanometer connected to a closed coil shows deflection when a magnet is moved either towards or away from the coil.

#### The motional EMF induced in a conductor is: (i) Inversely proportional to the magnetic induction (ii) Directly proportional to the velocity of the conductor

Correct! Wrong!

The motional EMF induced in a conductor is directly proportional to the velocity of the conductor.

#### Lenz’s law does not obey the law of conservation of energy.

Correct! Wrong!

Lenz’s law complies with the law of conservation of energy.

#### Unit of magnetic flux that is accepted internationally is ____.

Correct! Wrong!

The SI unit of magnetic flux is weber.

#### In electromagnetic induction, energy is conserved.

Correct! Wrong!

In electromagnetic induction, energy is conserved as the phenomena comply with the law of conservation of energy.

#### Which of the following work on the principle of electromagnetic induction?

Correct! Wrong!

An electric generator works on the principle of electromagnetic induction.

#### (i) When a conductor moves in a magnetic field, motional EMF is induced in the conductor. (ii) When a charge is moved in a magnetic field, Lorentz force acts on the charge.

Correct! Wrong!

Motional EMF is due to the motion of a conductor in a magnetic field. This is due to the Lorentz force acting on the free electrons in the conductor.

#### A galvanometer connected to a closed coil shows deflection

Correct! Wrong!

A galvanometer connected to a closed coil shows deflection when any magnet is moved towards it, because the magnetic field associated with the coil changes.

#### Lenz’s law is applicable only to the situations where a magnet is moved away from or towards a coil.

Correct! Wrong!

Lenz’s law is applicable only to all the situations where there is a change in magnetic flux with time linked with a coil, no matter whatever the method of achieving the change in the magnetic flux.

#### If the North-pole of a bar magnet is moved towards a coil, the magnetic flux through the coil ____.

Correct! Wrong!

If the North-pole of a bar magnet is moved towards a coil, the magnetic flux through the coil increases.

#### (i) When a bar magnet is moved away from a coil, a repulsive force is experienced. (ii) The EMF induced in the coil opposes the cause that produces it.

Correct! Wrong!

When a bar magnet is moved away from a coil, an unlike pole is induced on the face towards the near end of the coil and hence an attractive force is experienced. This is in accordance with Lenz’s law.

Class 12th Physics - 7 Electromagnetic Induction MCQs
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