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Electromagnetic induction

From Simple English Wikipedia, the free encyclopedia

Electromagnetic induction is where a voltage or current is produced in a conductor by a changing magnetic flux. It may happen when a magnet is moved in a solenoid, or when a solenoid is constantly moved in a stationary magnetic field, thus changing the magnetic flux.

Magnetic flux[change | change source]

When a coiled wire is introduced near a magnet, the magnetic lines of force pass through the coil. This causes the magnetic flux to change. Magnetic flux is represented by the symbol , therefore we can say that = BAcos(a) and the resulting unit will be , where T is the unit for magnetic field and is the unit for area.

The changing magnetic flux generates an electromotive force (EMF). This force moves free electrons in a certain way, which constitute a current.

Faraday's law[change | change source]

Michael Faraday found that an electromotive force is generated when there is a change in magnetic flux in a conductor.

His laws state that:


is the electromotive force, measured in volts;

is the change in magnetic flux, measured in webers;

is the change in time, measured in seconds.

In the case of a solenoid:


N is the number of loops in the solenoid.

Lenz's law[change | change source]

The negative sign in both equation above is a result of Lenz's law, named after Heinrich Lenz. His law states that the electromotive force (EMF) produces a current that opposes the motion of the changing magnetic flux.

Related pages[change | change source]