Magnets

The shopping list sticks to the fridge as if by magic, the flap of your tablet case snaps shut on its own, and a compass shows you the way in the forest. Behind all of this is the same invisible force: magnetism. Let us look at the rules it plays by.

North pole and south pole

Every magnet has exactly two poles: a north pole and a south pole. Clear rules apply between them: like poles repel each other, unlike poles attract each other. So if you hold two north poles together, you can feel them pushing apart. A north pole and a south pole, on the other hand, snap together. And what actually sticks to a magnet? Mainly iron, nickel and cobalt. That is why the magnet holds the note on the steel door of the fridge but not on aluminium, copper or wood.

Poles cannot be separated

You might think: if I break a bar magnet in the middle, I will hold the north pole in one hand and the south pole in the other. But that is not how it works. Each broken piece instantly becomes a complete magnet again with its own north and south pole. No matter how often you split it, you never get a single pole on its own.

The Earth is a magnet

Our planet is a giant magnet too. That is why a compass works: its small magnetic needle aligns with the Earth's magnetic field and points north. Strictly speaking it points to the magnetic north pole, which sits a little way off the geographic one. Sailors have used this for centuries. And magnets can even be switched on: when current flows through a coil of wire, it becomes an electromagnet. An iron core inside makes it especially strong. As soon as the current stops, the force is gone. That is how cranes in scrap yards lift car parts weighing tons and drop them exactly where they want.