Magnetic Fields

All magnets create a magnetic field, which is an area around a magnet where forces act on other magnets or magnetic materials. We can use magnetic field lines to represent a magnetic field.

These magnetic field lines always come out of the north pole and go towards the south pole. This is shown by the arrows, so make sure to include arrowheads as it shows the direction of the field lines. Magnetic fields are strongest near the north and south poles, which is shown by the concentration of the lines.

The distances between the field lines show how strong the magnetic field is.

  • The closer the field lines are, the stronger the magnetic field is – So the magnetic field lines are closer together at the poles.
  • The further the field lines are, the weaker the magnetic field is – So the magnetic field lines are slightly further apart as you go away from the magnets.

Finding Magnetic Fields

Two ways that magnetic field lines can be shown are by plotting compasses and by using iron fillings.

Plotting compasses

Plotting compasses is one way to show magnetic field lines.

Here we have many small compasses surrounding the bar magnet. As you can see, the north pole of the compass is pointing towards the south pole at all times. if you extend the lines, it will start to look like the original magnetic field diagram, going out of the north pole and into the south pole.

Iron filings

To show magnetic field lines, we can also place a bar magnet in a pile of iron fillings. The iron fillings will sort themselves along the magnetic field lines.

Here we can see the iron fillings showing the magnetic field around the bar magnet.

Magnetic Field Lines Of Attraction

Opposite poles

We can use the magnetic field lines of two magnets to show how opposite poles attract.

Here we can see the field lines of the two magnets interacting. As we know that field lines travel from north to south, it is easier to understand why there is an attraction between opposite poles.

Like poles

Now let’s look at like poles. For example, two north poles next to each other.

As the magnetic field lines are trying to go from north to south, the magnets will repel each other. The magnetic field lines of the magnets are not touching because they are trying to reach the south pole.

This means that when like poles are placed together, there is a repulsion.