Monday, April 26, 2010

Electromagnetism

Electromagnetism is the science of the properties and relationship between electric currents and magnetism.
An electric current creates a magnetic field and a moving magnetic field will create a flow of charge.

A bar magnet produces magnetic fields the around it.
Magnetic fields also can be produce by an electric current in a wire.
If you hold a compass near a wire through which current is flowing, the needle on the compass will be deflected.

Electromagnet is a temporary magnet. It is made by winding a coil of insulated wire round a soft iron core.

The magnetic field produced by an electric current is always oriented perpendicular to the
direction of the current flow. When we are drawing directions of magnetic fields and currents,
we use the symbol ⊙ and .

The symbol⊙ for an arrow that is coming out of the page and
the symbol for an arrow that is going into the page.

It is easy to remember the meanings of the symbols if you think of an arrow with a head and a
tail.

When the arrow is coming out of the page, you see the head of the arrow (⊙).
When the arrow is going into the page, you see the tail of the arrow ().

There is a simple method of showing the relationship between the direction of the current flowing in a conductor and the direction of the magnetic field around the same conductor. The
method is called the Right Hand Rule.

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