Magnetic hovering

How does the exhibit work?

Gently hold the ball under the electromagnet. The ball does not need to touch the electromagnet. After a few seconds, gently release the ball. The ball keeps floating in the air.

What is the science behind it?

Is it a bird? Is it a plane? No, it's a floating ball.

We call this floating 'magnetic levitation', or maglev for short. All you need is a magnet (in the ball) and an electromagnet (in the tube). A magnet is always magnetic. An electromagnet is only magnetic if you pass current through it. It can therefore be switched on and off.

Now hold the ball under the tube. Ta-da, it floats!

What exactly is happening?

Gravity pulls the ball down. But the attraction between the magnet and the electromagnet pulls the ball up. A sensor in the tube detects if the magnet gets too close to the electromagnet. Then, the electromagnet switches off. The attraction disappears and the ball drops. The electromagnet switches on again and up goes the ball. And that happens again and again. Since the electromagnet turns on and off at the speed of lightning, the ball keeps floating.

As an attentive visitor, you may have noticed that the ball actually sticks to the tube if you hold them together. How can that happen if the electromagnet goes off when you get too close?

This is simply because the electromagnet contains iron. The magnet in the ball is attracted if it gets too close.

Maglev in trains

There are trains that float 10 cm above the rails. These maglev trains whizz above a track of electromagnets. There is no friction from metal on metal, so the trains can go much faster. The fastest has reached 603 km per hour!