Magnets are one of the
fundamental items in physics. This page is designed in order to
provide a general overview of magnets and their uses as well as
an in depth look into certain aspects of magnetism.
We all know certain situations where magnets
are used, hanging things on a refrigerator for example. But other
applications are much more useful in our society. They are used
in all kinds of speakers, and in many computer parts including
hard drives and floppy drives ( for recording and reading purposes).
Perhaps a more common use that goes unnoticed is the magnetic
strip on credit and debit cards. These have a certain magnetic
makeup, that is why you are to keep them away from other magnets.
Magnets are also used in many motors, in such items like a dishwasher,
DVD and VHS players, and a pager or cell phone vibrator. For a
more complete list visit http://my.execpc.com/~rhoadley/magencyc.htm
.
Magnets are all dipoles, that is they all have
both a north and a south pole. No known magnetic
monopoles exist. Looking at magnets from a basic point of
view, opposites attract and similars repel. Magnetic field lines
always move from the north pole to the south pole, we will discuss
this later.
This picture shows "donut" magnets attracting
and repelling. (Image Courtesy of http://www.kingsford.org/khsWeb/rfs/elemsci/magnet.html)
Some of the major contributors to magnets are
men like Hans Christian Oersted, James Clark Maxwell, William
Scoresby, Michael Faraday and Joseph Henry.
Hans Christian Oersted experiment with a wire
carrying a current and a compass led to much of what we know about
Magnetic Fields.
James Clark Maxwell discovered relationships between electricity
and magnetism many of which are used in the Electromagnetic Theory.
More information on the relationship between magnets and electricity
can be found here.
William Scoresby used the Earth's magnetic fields
to produce powerful magnets.
Michael Faraday and Joseph Henry are reported
to have simultaneously discovered electromagnetic induction, which
is the effect whereby the relative motion of a magnet and an electric
coil produced a current.
There are three types of magnets. Permanent,
temporary, and electromagnets. Permanent magnets are the most
common ones. Once they are magnetized they stay so (although they
can lose much of their magnetic force). They can be metals found
in nature. Temporary magnets hold the properties of a magnet while
in a magnetic field, but lost these properties once the field
goes away. An example of this would be a paper clip that is charged
and can act like a magnet for a short while. Electromagnets are
wires wrapped around a metal center(usually iron). The wires have
a current flowing through them. An example of this would be a
nail with wires wrapped around it and connected to a battery.
The nail would then be able to pick up metallic objects.
A basic film on understand magnets.(http://www.mmem.spschools.org/2F.9798/Magnets/MagnetClips/DestroyMagnetMovie.html)
Magnets are very complex and yet so useful and
common in nature. Because this topic is so extensive this page
is intended to cover only a few subject matters relating to magnets.
For an example on how magnets DO NOT work watch
this funny
movie.