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Copper in health
 Magnetic fields 
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.

Interactive graphic of magnets
Picture 2. Two bar magnets will attract or repel, depending on which way they are facing.

What do the poles do?
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.

Interactive graphic of iron filings experiment
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:

  1. place a piece of cardboard over the magnet
  2. gently sprinkle some iron filings onto the cardboard
  3. tap the cardboard so that the iron filings line up with the magnetic field.
  4. look for the pattern made by the iron filings

Which way is the magnetic field going?

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.

Artwork of magnetic field lines
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.

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Question 1
The pictures below show some magnets close to each other. In each case, they might attract or repel. Decide what will happen and click in the box of your choice.
Magnets attract repel
a) A north pole and piece of steel. Artwork of magnets for question
b) a south pole and a piece of steel Artwork of magnets for question
c) a north pole and south pole. Artwork of magnets for question
d) a north pole and north pole. Artwork of magnets for question
e) a south pole and an unmarked pole with field lines as shown. Artwork of magnets for question