Electromagnetic induction
production of voltage by a varying magnetic field From Wikipedia, the free encyclopedia
production of voltage by a varying magnetic field From 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.
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.
Michael Faraday found that an electromotive force is generated when there is a change in magnetic flux in a conductor.
His laws state that:
where,
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:
where,
N is the number of loops in the solenoid.
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.
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