Electromagnetic induction

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 

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 

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.

 Lenz's law 
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 
Electromagnetism
Inductor
Transformer

Category:Electromagnetism