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The attractiveness of magnets

Many people know that in an electromagnet, the magnetism comes from the electric current running through the wires. But how then, they ask does a permanent magnet work, when there is no current?

The answer is that magnetism comes from the movement of electrons. In a permanent magnet, even though there is no electrical current, there are still electrons and they are still moving.

Electrons little charged particles orbiting round a nucleus (made up of protons and neutrons) in much the same way that planets orbit the sun. But the electrons cannot be just anywhere. They are whizzing round the nucleus at something close to the speed of light (186,000 mps). The important thing here is that they are grouped together in shells. Imagine earth and another planet (its “doppelganger”) on the other side of the sun. or imagine a group of eight planets all orbiting the sun from the same distance in the same plane or ring, so that they never get near each other.

Now in addition to this the planets spin. So imagine earth and its opposite planet spinning, but in opposite directions. Electrons too have a characteristic called spin and in atoms they form pairs with opposite spin. No paired atoms in any given atom can have the same spin. This is known as Pauli’s Exclusion Principle, after Wolfgang Pauli, the theoretical physicist who discovered it. Now when electrons spin, they create magnetic fields. However because the electrons are in pairs that spin in opposite directions, their magnetic fields cancel each other.

However what happens if some of the atoms in are unpaired? Remember it is only paired atoms that have the same spin. The answer is that if an atom has unpaired electrons, then there is nothing to cancel out the magnetism that can be caused by the spins of the unpaired electrons. These electrons are said to have an orbital magnetic moment. This is a force. The sum of the magnetic moments is the magnetic moment of a magnet as a whole.

That does not mean that such materials are all magnets. Their magnetic moments may cancel each other out. But if they are magnetised by the spinning of the earth when the earth’s crust was hot, then groups of atoms with parallel spins will have lined up. Then, when the earth cooled down, the alignment remained. It is those materials that are naturally magnetic. However soft metal can also be turned into a permanent magnet by applying a strong electromagnetic field to it. And the substance that are best attracted to magnets are the same substances that can be magnetised.

So when you buy a magnetic bracelet from a magnetic products store, you buying an object made up of parts that may have been created in the earth’s crust but more likely has been manufactured in a mass production process that mimics the effects of nature.