Not all metals are magnetic

Wrong Track: All metals are magnetic, magnets will stick to any metal!

Right Lines: Most metals are not magnetic. The most common magnetic metals are iron, steels with a high iron content, nickel and cobalt.

Metals as electrical conductors

Thinking about the learning

The classification of materials into electrical conductors and insulators in primary school suggests to children that metals are special when it comes to electricity. It is not therefore surprising that the same classification is transferred in children's thinking to the topic of magnetism. Metals are expected to be magnetic and non-metals are expected to be non-magnetic.

Gravity is not related to magnetism

Wrong Track: We are pulled down onto the Earth's surface by gravity. Gravity works because the Earth is like a giant magnet which attracts things to the surface.

Right Lines: Gravity is not related to magnetism.

Forces associated with the Earth

Thinking about the learning

This is a common conflation. Children know that magnets are associated with a magnetic force and that there is magnetism associated with the Earth. When a mechanism is sought to explain gravity, magnetism therefore becomes an obvious candidate.

The gravitational force and magnetic force are different in nature, as an example shows.

Imagine two magnets: the magnetic force between them will and two attracting and repelling (depending on the orientations), whilst the gravity force between them will always be attractive.

Now imagine two non-magnetic bars of identical mass to the magnets: there will be no magnetic force between them (whatever the orientation of the bars), but the gravity force between them will still always be attractive, and of the same value as before.

Magnets act-at-a-distance

Wrong Track: Magnets need air to work. If there's nothing between them they can't attract or repel each other.

Right Lines: The magnetic force requires no medium to act at a distance. Magnets will attract and repel just as well through a vacuum as in air.

Action at a distance

Thinking about the learning

Some pupils will argue that air is needed to enable magnets to attract and repel each other.

This line of argument is certainly incorrect, but it is also understandable in that it suggests a medium through which the magnets can act at a distance.

Thinking about the teaching

You might want to challenge this wrong track thinking directly in your teaching by setting up a demonstration. This might involve placing a piece of iron in a bell jar, removing all of the air from the jar with a vacuum pump and seeing whether the iron is still attracted to a powerful magnet held outside the jar. Ask for pupil predictions before you start removing the air.

Losing magnetism

Wrong Track: The magnet sends out electricity to make it attract and repel. That's why it loses its strength.

Right Lines: Magnets wear out as their internal mini-magnets become disordered, pointing in all directions.

Thinking about magnets wearing out

Thinking about the learning

In real life, permanent magnets do wear out and lose their magnetism. Pupils sometimes associate this with the magnet giving something out to make it attract and repel.

Thinking about the teaching

This idea of the magnet sending out electricity is incorrect, but the question as to why magnets wear out is a good one. It's best thought of in terms of the mini-magnet model introduced in the Physics Narrative.