Electromagnetic Induction

What is electromagnetic induction?

• The production of a magnetic field by an electric current.

• The production of an induced e.m.f. in a conductor when the magnetic flux through it changes.

• The creation of a magnetic field by a permanent magnet.

• The generation of electric current by a battery.

Magnetic flux is defined as

• The product of magnetic field strength and area.

• The scalar product of magnetic flux density and the area vector.

• The vector product of magnetic field and area.

• The product of magnetic field and current.

The unit of magnetic flux is

• Tesla (T)

• Weber (Wb)

• Henry (H)

• Ampere (A)

If the angle between the magnetic field and the area vector is 90°, the magnetic flux is

• Maximum

• Minimum

• Zero

• Equal to the magnetic field strength

Faraday's law states that the induced e.m.f. is proportional to

• The rate of change of magnetic flux.

• The magnitude of the magnetic field.

• The area of the coil.

• The number of turns in the coil.

Lenz's law states that the direction of the induced current is such that it

• Enhances the change in magnetic flux.

• Opposes the change in magnetic flux.

• Follows the direction of the magnetic field.

• Is always in the same direction as the applied current.

A straight conductor of length 0.2 m moves at a speed of 10 m/s perpendicular to a magnetic field of 0.5 T. The induced e.m.f. is

• 0.1 V

• 1.0 V

• 10 V

• 100 V

A coil of 100 turns has a magnetic flux of 0.02 Wb passing through it. If the flux changes to 0.08 Wb in 0.1 seconds, the induced e.m.f. is

• 6 V

• 60 V

• 600 V

• 6000 V

The self-inductance of a coil depends on

• The current flowing through the coil

• The number of turns, area, and permeability of the medium

• The resistance of the coil

• The applied voltage

The energy stored in an inductor is given by

• U=½ LI²

• U=½​ CV²

• U=½ ​QV

• U=½IR