Magnetism
Physics: IB Diploma Higher Level, topic 4.6.1
Magnetism
Magnetism describes the ability of magnets to attract (pull towards) and repel (push away) other magnets without touching them.
Attraction
- Magnets have a north pole (N) and south pole (S).
- If two magnets are close enough to each other, then the south pole of one magnet will attract the north pole of the other magnet.
- This is an example of a non-contact force.
Repulsion
- If one magnet is turned so that both south poles (or both north poles) are close together, then the magnets will repel each other.
- Opposite poles on a magnet attract and like poles on a magnet repel. This is an example of a non-contact force.
The poles of a magnet
- A magnet's poles are where the magnetic forces are strongest.
- A bar magnet that is snapped in half, both halves will have a north and south pole.
Magnetic Materials
Iron, nickel, and cobalt are the only pure metals that can be turned into a magnet. These metals are “ferromagnets”.
Properties of ferromagnets
- Ferromagnets, like iron, don’t always act as magnets.
- For example, a normal piece of iron won’t attract (pull) or repel (push) another piece of iron.
- But ferromagnets are attracted to a magnet if they are close enough to the magnet.
Properties of ferromagnets
- Ferromagnets can be attracted by a magnet, but can’t be repelled by a magnet.
- Only two magnets can repel each other.
- Non-magnetic materials will never be attracted to magnets.
- Permanent magnets are always magnetic, even when they are not near other magnets.
- They produce their own magnetic field.
Test yourself on Magnetism
What are the poles of a magnet?
Which of the following are true?
Which of these is not a magnetic material?
Which of the following are true?
Name the four well known magnetic materials