Download A Magnet is an object with a magnetic force or field that attracts or

A Magnet is an object with a magnetic force or field
that attracts or repels objects. A magnet’s property of
attracting material is called magnetism.
Magnetism is a force that acts on moving electric
charges and magnetic material. Iron and steel are
attracted to a magnet.
Not all metals are attracted to a magnet.
Copper, aluminum, and gold are examples of metals
that are NOT attracted to a magnet.
There are different kinds of magnets.
Ex. bar magnets, horseshoe magnets, circle magnets,
and donut magnets (circle with a hole), wand magnet
People have many uses for magnets in their
everyday lives. They are used to hold things on
refrigerators, to close cabinet doors, in a compass, in toys,
and to pick up pins or thumbtacks to avoid being stuck. A
magnetic screwdriver makes it easier to hold screws in
place. MRI’s use magnets to produce pictures of the inside
of the body which help doctors identify injuries to muscles
and tissues.
A Maglev (Magnetic Levitation) train runs on electricity
and uses magnetic force to float slightly above the rails or
tracks because the magnets are repelling each other. These
quiet trains are not slowed down by friction and travel
superfast (up to 300 miles per hour).
There are two kinds of magnets:
1. A permanent magnet is made in a factory and keeps its
magnetism for a very long time.
2. A temporary magnet does NOT keep its magnetism for
a very long time. A temporary magnet can be made by
stroking a nail many times, very quickly with a permanent
magnet. It will then remain magnetic for a very short time.
Magnets have a North and South Pole.
Like poles (N-N, S-S) of magnets will repel or push
away from each other.
Unlike poles (N-S, S-N) will attract or pull toward
each other. (Opposites attract)
A magnet has a force field that you can’t see. The
space in which the force of a magnet can act is
called its magnetic field. A magnet’s magnetic field
spreads out in all directions throughout the space
around the magnet.
A magnet’s magnetic force is strongest at its poles
and gets weaker away from its poles.
Scientists have learned the Earth is a giant magnet.
Earth’s center is made of mostly iron and the
spinning of the Earth on it axis has turned Earth into
a giant magnet. The spinning has magnetized the iron
at its center
Lodestone is a naturally magnetic rock found at or
near Earth’s surface. Thousands of years ago, people
discovered that when lodestone was hung by a string,
one end always pointed north. This was used by
Chinese sailors to tell what direction they were
sailing. Today a compass is based on the same idea. A
compass uses a magnetized needle which is allowed
to swing freely. The compass needle points to the
Earth’s magnetic north pole.
Earth has two sets of poles: 1. Geographic 2. Magnetic
They are NOT the same. The Earth’s magnetic north
pole can be 500-1200 miles away from its geographic
north pole.
Ordinary magnets work without an electric current.
Electric circuits work without magnets.
Hans Christian Oersted discovered there was a
relationship between electricity and magnetism which
led to the invention of the electromagnet.
An electromagnet is a magnet that only works
when electricity is provided. To make an
electromagnet, you pass an electric current through a
coiled wire. The moving electric current creates a
magnetic field. The wire loses its magnetism when
the current is stopped.
Ways to make an electromagnetic stronger:
1. Coil the wire around an iron core Ex.an iron nail
2. Add more coils or wire (the more coils, the
stronger, the magnetic field)
3. Increase the amount of electric current running
through the wire
Electromagnets are useful because you can turn them
off when you do not want them to attract objects.
There are electromagnets in doorbells, computers,
and DVD players and motors in fans and blenders.
Moving a magnet within coiled wires produces
electricity. A generator is a machine that
produces electric energy by turning coils of wire
around powerful magnets. A generator turns the
energy of motion into electrical energy.
Wind or water can power these generators.