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Magnets and Magnetism
8th grade science
Properties of Magnets…
2000 years ago the Greeks discovered
a mineral that attracted things made
of iron.
 They named this mineral Magnetite
because it was discovered in Turkey
near the town call Magnesia.
 Magnet is any material that attracts
iron or things made from iron.
 Magnetic Poles one of two points,
such as the ends of a magnet, that
have opposing magnetic qualities.

Properties of Magnets…
All magnets have a North and South
Pole. One part of the magnet will
always point to the North while the
other will always point to the South.
 The poles of magnets are always in
pairs. You will never find a magnet
with just one pole.
 Magnetic Force is the force of
attraction or repulsion generated by
moving or spinning electric charges.

Properties of Magnets…
Magnetic field is the region around a
magnet in which magnetic forces can
act. The shape of a magnetic field can
be seen below.
 The closer together the field lines are,
the stronger the magnetic field is.
The magnetic field is strongest at the
poles

The Cause of Magnetism
 Magnets
can pick up things
like paper clips and nails
but why cant it pick up
things like paper, plastic,
pennies, or aluminum
foil?
Atoms and Domains…
All matter is made of atoms.
 Electrons are the negatively charged
particles of the atom.
 Electrons move around and make or
induce a magnetic field.
 Materials like copper & aluminum
aren’t magnetic because the individual
atoms cancel each other out.
 Materials like iron, nickel, & cobalt
have their atoms grouped in tiny areas
called domains. These domains line
up to make N. & S. poles.

Losing Alignment
If the domains in an object are randomly
arranged, the magnetic fields of the
individual domains cancel each other
out, and the object has no magnetic
properties.
 If most of the domains in an object are
aligned the magnetic fields of the
individual domains combine to make the
whole object magnetic.
 Dropping or hitting a magnet can change
the domains.
 Placing a magnet near a stronger magnet
or increasing the temperature
significantly will also change the
magnetic properties.

Making Magnets
Magnets can be made from iron,
cobalt, or nickel if you can simply line
up the domains.
 An iron nail can be magnetized if you
rub it in one direction with one pole of
a magnet.
 Electric current can also be applied to
metal causing it to become
magnetized.

Cutting a Magnet
 Would
cutting a magnet in half
leave you with a North Pole
magnet and a separate South Pole
magnet?
 If you cut a magnet into two
separate pieces, each piece will
still be a magnet with a North
Pole and a South Pole.
Kinds of Magnets
Ferromagnets are magnets made
from iron, cobalt, nickel, or
mixtures of these metals.
 Electromagnets are magnets
produced through the use of a
strong electric current.
 The core of an electromagnet is
usually made from iron.

Earth as a Magnet
Man has used a compass to find his
way for thousands of years.
 A compass is simply a freely
floating/spinning magnet.
 The painted portion of the needle on a
compass is a North Pole magnet.
 A compass needle points North
because the magnetic pole of Earth
that is closest to the geographic North
Pole is actually a magnetic south pole.

Earth as a Magnet
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English physician William Gilbert said in
1600, “Earth behaves as if it has a bar
magnet running through its center and the
poles of this imaginary magnet are located
near Earth’s geographic poles.”
The Earth doesn’t really have a bar magnet
running through it though.
Scientist believe the Earth’s magnetic field is
caused by movement of electric charges in
Earth’s core.
Earth’s inner core is made of iron and nickel
and is under extreme pressure.
The outer core is liquid and flows as the
Earth rotates, which causes electric charges
to build and create a magnetic field.