A magnet will pull on some metals like iron. We say these metals are magnetic. We can also make a magnet from soft iron. This magnet will have two poles - a north and a south.
If we bring the north pole of one bar magnet up to the south pole of another one, they will attract each other.
We say that:
Opposite poles attract.
However, if we bring a north pole up to another north pole, they will be forced apart. We say that they repel. The same happens with two south poles.
We say that:
Like poles repel.
What is a magnetic field?
A magnet does not have to be touching another magnet to pull it or push it. The force from the magnet reaches out. It is an invisible force that works at a distance. We say that there is a magnetic field around the magnet. The magnetic field is the region in which a magnet's force works.
The magnetic field is invisible. We need to use some clever tricks to see its shape.
Picture 3. We can use iron filings to show the look of the magnetic field.
How can we see the magnetic field?
You can see the shape of the magnetic field using iron filings:
The iron filings tell us the shape of the magnetic field. However, it's also useful to know which way the field is going - i.e. will it attract or repel a north pole of another magnet.
We can find this out using a small compass. The compass needle is itself a small magnet. Its arrow is a north pole. So the compass points away from the north pole of the magnet.
Picture 4. The field lines around a bar magnet.
Magnetic field lines
We can show this on a diagram of the magnetic field using field lines. Notice that the magnetic field lines
point away from the north pole and
point towards the south pole
and
never cross over each other
only come out of the ends of the magnet
are closest together where the field is strongest - e.g. near the poles.
The arrows on the field lines tell us which way another north pole would move. A south pole would be pulled in the opposite direction to the arrows.
