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The Pull Of Magnets
by Charles Linrette
http://www.flmagnet.com
Most of us have seen magnets and know what they do, but did
you know there are two kinds of magnets? One kind of magnet
is called a permanent magnet and these do not need the help
of outside influences to give them power. The other kind of
magnet is called electromagnets and these do need the help
of outside influences to generate their power.
Most objects containing metal or iron are attracted to
magnets because these materials have some kind of
permeability in them. Even magnets are attracted to each
other on one side, turn them over though and they repel
each other. Water is not attracted to magnets because it
has no permeability to it. To measure a magnets strength
it's measured by a unit called a Telsa, named after an
electrical engineer Nikola Tesla, who spent his time
working with magnets.
If a magnet is brought close enough to another magnet,
their fields will begin to interact in one of two ways. If
two magnets' north poles are brought together, the magnets
will repel one another. If the north pole of one magnet is
brought to the south pole of another magnet, the magnets
attract one another, holding true to the principle that
opposites attract. Objects can be magnetized or
demagnetized. Ferromagnetic materials can be magnetized by
placing them in an external magnetic field, causing them to
retain some of the magnetism when removed, retaining some
of the magnetism on removal. One way that objects can lose
their magnetism is exposure to high heat.
Magnets function as transducers, meaning they transform
energy from one form to another, without any permanent loss
of their own energy. For example, loudspeakers rely on a
combination of a permanent magnet and an electromagnet.
Fundamentally, a speaker is a device that converts electric
energy (the signal) into mechanical energy (the sound).
Some electric motors, much like loudspeakers, rely upon a
combination of magnets. A generator is the reverse of
loudspeakers and motors. They convert mechanical energy
into electric energy.
Magnets are an important part of our daily lives. Their
contribution is often overlooked because they are built
into devices and usually are out of sight. For example, VHS
tapes contain a reel of magnetic tape that contains encoded
video and sound. Similarly, computer floppy disks record
data through a thin magnetic coding. All credit, debit and
ATM cards have a magnetic strip containing the necessary
information to contact an individual's financial
institution and connect to their accounts. Common
televisions and computer monitors rely in part on an
electromagnet to generate an image. Magnets also serve as
essential components in such everyday items as electric
motors, loudspeakers, microwave ovens and automobiles.
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