Magnetic bridge

How does the exhibit work?

Place the rondelles between the two large, curved parts. You can also try pulling them out between them.

What's the science behind it?

The two large, curved parts are magnets. Not just any magnets, but very strong, permanent magnets. This simply means that they are always magnetic. Around each magnet is an invisible, magnetic field. This attracts iron objects, like the rondelles.

Take a rondel in each hand and hold them against each other. Do they attract each other? No, they are not magnetic. But if you hold them against the big permanent magnets, they do become magnetic. Then they stick to each other. They are temporary magnets.

Crazy, isn't it! That's because in the rondelles there are lots of tiny, magnetic areas - kind of like tiny mini magnets. Normally, these are criss-crossed. As a result, the rondelles are not magnetic. But do you hold them near a permanent magnet? Then the areas all point in the same direction. And so the rondelles do become magnetic!

Want to know more about magnets? Have a look at the Iron fillings dance or Magnetic hovering.

Magnet earth

The earth is actually a giant magnet. That's because, in the core of the earth, there is a swirling hot metal mass that moves continuously, generating a powerful magnetic field. As a result, your compass needle always points north.