My dictionary says that electromagnetism is "the phenomena associated
with electric and magnetic fields and their interactions with each
other and with electric charges and currents". This is basically just a
long way of saying that electricity and magnetism are very closely
related.
A great example of this is an electromagnet. You can build one of
these at home by wrapping a fine insulated electrical wire many times
around a nail, and then hooking it up to a battery. The nail will be
turned into a temporary magnet. The principle behind this says that
magnetic fields are produced by moving electric charges (called
currents). In this case, there is a current flowing in the wire wrapped
around the nail, and it produces a magnetic field along the direction
of the nail. The nail itself is not needed to produce this field, but
helps to contain and guide the field so you can (for example) pick up
some paper clips with it.
Going the other way, you can create an electrical current by using
a changing magnetic field. You can show this using a small coil of
electrical wire hooked up to a very small light. Take a bar magnet and
move it back and forth through the middle of the coil. (It won't work
if you just hold the magnet still, since it has to be a
changing
magnetic field.) You should be able to see the light turn on because of
the current that is induced in the wire. This is the same principle
that makes electric generators possible.
-Tamara
(published on 10/22/2007)
