What are Magnets?
Magnets are objects that produce a type of energy called
magnetic fields. All magnets possess a property called polarity--that
is, a magnet's power of attraction is strongest at its opposite ends,
usually called the north and south poles. The north and south poles attract
each other, but north repels north and south repels south. All magnets
Magnets come in different strengths, most often measured
in units called gauss (G). For comparison purposes, the Earth has a magnetic
field of about 0.5 G; refrigerator magnets range from 35 to 200 G; magnets
marketed for the treatment of pain are usually 300 to 5,000 G; and MRI
(magnetic resonance imaging) machines widely used to
diagnose medical conditions noninvasively produce up to 200,000 G.1
The vast majority of magnets marketed to consumers for
health purposes (see the box below) are of a type called
static (or permanent) magnets. They have magnetic fields that do not change.
of Products Using Magnets
The other magnets
used for health purposes are called electromagnets, because they generate
magnetic fields only when electrical current flows through them. The magnetic
field is created by passing an electric current through a wire coil wrapped
around a magnetic core. Electromagnets can be pulsed--that is, the magnetic
field is turned on and off very rapidly.