Forces and Motion | Electricity and Magnetism

Differentiating between electric and magnetic forces

Teaching Guidance for 5-11 11-14 Supporting Physics Teaching

Electric and magnetic forces

Wrong Track: The positive pole of this magnet attracts the negative pole of the other one.

Right Lines: Both magnetic and electric forces can attract and repel, but the the mechanisms to account for these interactions are different; in one case involving magnetic poles and in the other case involving electrically charged objects.

Explaining the difference

Thinking about the learning

The problem here is that pupils confuse the charge story of electric forces with the pole story of magnetic forces. This is hardly surprising since opposites attract and likes repel is a common mantra of the science classroom.

The same pattern of attraction and repulsion is found both for magnets and for electrically charged objects. Two like poles (two norths or two souths) repel each other, whilst opposite poles, a north near a south, attract. However, you should take care not to mix up attraction and repulsion between poles with attraction and repulsion between opposite or similar electrically charged objects.

Here are some children working in this area:

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Thinking about the teaching

The field concept can be used to describe the action-at-a-distance effect in both electric and magnetic situations. Repulsive and attractive forces are also evident in both cases.

However, we interpret electric forces to be the result of the separation of positively and negatively charged particles. Magnets, on the other hand, are not charged. The force between magnets can be accounted for in terms of the effect of an alignment of the atoms within the magnet. Each atom might be considered to be a mini magnet. When these atoms line up together their combined effect is strong enough to reach out beyond their immediate location – the magnetic field, a force field, exists around the magnet.

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