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What do you already know about magnets?

Magnetism

The property of attraction

What is a MAGNET?• Any material that attracts iron or

contains iron• Magnetism was first discovered by

the ancient Greeks in a town called Magnesia (now located in Turkey).

People noticed that certain stones containing iron attracted metal. They were called Lodestones.

Lodestone came from “lodestar” or leading star, the name given to

the North Star - Polaris

How do magnets work?

• One part will always point north when allowed to swing freely.

• Magnets have a north and south pole, or end.

• Opposite ends attract, like ends repel.

• The attraction and repulsion is called the magnetic force.

Magnets do not have to touch in order to attract or repel each other. They are

surrounded by a Magnetic Field.

Like sides repel; Opposite sides attract. These lines are called magnetic field lines.

Notice how the field lines come out of the NORTH end and enter the SOUTH

end.

Magnetic Field Lines:

• They form complete loops from 1 pole to the other.

• They cannot be directly observed.• They never cross.• They spread out as they get

farther from the poles. The closer they are together, the stronger the magnetic field.

What did you learn today?

Do Now:

What do you know about magnetic field

lines?

Inside a Magnet

Electrons in atoms behave as if they were spinning in a cloud around the nucleus. Spinning electrons create their own magnetic field. Paired electrons in an orbital (“a room”) cancel out each other’s magnetic field (weak magnetism). But atoms with single electrons have strong magnetism.

Atoms with a strong magnetic property have magnetic fields aligned in the same

direction called a magnetic domain.

Materials that have magnetic domains that are aligned are called

ferromagnetic

materials (iron attraction).

The most common magnets are made from ferrite that can be easily shaped into many

forms.

How are magnets made?

http://www.youtube.com/watch?v=lRux43wwunU

Temporary v. Permanent magnets

• If you rub the material you want to magnetize with one pole of a strong magnet, you can create a temporary magnet. (loses its magnetism quickly)

This process causes the domains of the unmagnetized material to line up in the same direction as the magnet, creating a magnetic field.

A permanent magnet is harder to magnetize but retains its magnetism for long periods of time. However, they can lose their magnetism by either hitting them hard or dropping them. The vibrations that are caused will shake up the magnet’s atoms causing the domains to become knocked out of alignment.

What happens if magnets are broken in half?

What did you learn today?