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Physics - Electromagnetic induction

Electromagnetic induction

Just as an electric current is able to produce a magnetic field, magnetic

fields can be used to create an electric current. When a current is induced

using a magnetic field, we say electromagnetic induction [1] has occurred.

Faraday [2]discovered that whenever the amount of a magnetic field that is

passing through a loop of wire is altering, a electric current is induced.

There a number of ways in which a loop can be made to experience a changing

magnetic field:

* a loop could be dragged into or out of a magnetic field

* a loop could be spun in a magnetic field

* a loop could be kept stationary and the strength of the field increased

or decreased

* a loop could be altered in size while in a magnetic

Since there were a number of arrangements that could result in an induced

electric current, Faraday came up with an equation that would explain the

size of the induced current in any situation. To do this, the term magnetic

flux was invented. Flux is defined as the product of the magnetic field and

the area of the loop that is perpendicular to that field.

Once flux is defined as shown, it can simply be stated that

electromagnetic induction of a current occurs whenever there is a change in

flux. This statement covers all possible ways of creating electromagnetic

induction. The size of the induced EMF [3](electromotive force or voltage)

depends upon

* the number of loops of wire

* the rate at which the flux value is changing.

The negative sign in the formula is a reminder of Lenz's law which states

that the direction of the induced voltage is such that it opposes the

change of flux that is occurring. A mechanism for determining the direction

of the induced voltage is discussed later.

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[2] http://alison.com/#

[3] http://alison.com/#

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