Magnetism and air
Teaching Guidance for 5-11 11-14
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.