A model of magnets
Physics Narrative for 11-14
Building a model of magnets – putting mini-magnets together
Imagine two bars of iron placed side-by-side on a table. One of them is a bar magnet, the other is not. From the outside it is impossible to tell which is which, just by looking. How might we imagine the difference between the two (which seem to be identical bars of iron) by thinking about their internal structure?
Inside any magnetic material, such as iron, we can imagine each atom or molecule to be a very small magnet or mini-magnet. So a magnet is made of lots of smaller magnets. You can do this on the bench top, by putting magnets together.
On the laboratory bench, you can do this with just two magnets,
With four magnets,
Or with 10 magnets.
In your imagination, you can extend this to very many mini-magnets, taking the large magnet apart and putting it together again.
Building a model of magnets – aligning mini-magnets
When the material is not magnetised, we can imagine that there is no pattern to the lay-out of the mini-magnets. In other words they point in all directions.
When the material is magnetised, the mini-magnets become aligned so that they all point in the same direction and the object becomes a magnet.
The mini-magnets are a way of thinking about what is happening during magnetisation. We'd suggest encouraging pupils to
think about it like this!. Science is full of such models which allow us to imagine what is happening, both to help us get a feeling for what is going on and to help us develop expectations.