Question: how do magnets work?

Sheila Kanani answered on 16 Mar 2011:

Hi thegame!

Great question coz you think it’d be a really simple answer as we use magnets every day, but it isn’t!

People have known about magnets for thousands of years and they’ve been using them, for example as compasses, for almost as long. The ancient Greeks and Romans knew as well as we do that lodestone (an iron-rich mineral) can attract other pieces of iron, while the ancient Chinese were using magnets for their practise of Feng Shui. Science can sometimes be slow to catch up! We’ve only really discovered how magnetism works in the last century, since inside an atom was first explored.

A magnet is any object that has a magnetic field. It attracts ‘ferrous’ objects like pieces of iron, steel, nickel and cobalt. Electricity and magnetism are really just two sides of the same coin: “electromagnetism”. Once scientists would have said magnetism was the strange, invisible force of attraction between certain materials; today, we’re more likely to define it as a force created by electric currents.

There are a number of ways to describe why magnets work.
The one I’m going to use is called “Domain Theory”

Imagine a bunch of cows with black faces and white bottoms. On rainy days the cows just like to huddle any old how so the black and the white colours all get jumbled up. One black head could be pointing north while the one next to it is pointing south, east, or west. Overall, the black bits and the white bits are all jumbled up so there is no pattern.

The next day it is sunny and all the cows face the Sun because it is warm. This means all the black heads face the Sun and all the white bottoms face the other way. Can you see what’ll happen? You get a lovely perfect pattern of black and white. Now imagine each cow is a magnet, their black heads are North poles and their white bottoms are South poles.

If you look at the group of cows, the side towards the Sun will be like a giant north pole and the back of the group a huge south pole!

What happens with these cows is what happens on a tiny scale inside magnetic materials. According to the domain theory, something like an iron bar contains lots of tiny pockets called domains. Each domain is a bit like a cow with a magnet inside. The iron bar is just like the field with the cows in. Normally, all its cows are arranged randomly and there’s no overall magnetism: the iron is not magnetized. But arrange all the cows in order, make them all face the same way, and you get an overall magnetic field: hey presto, the bar is magnetized. When you bring a magnet up to an unmagnetized iron bar and stroke it systematically and repeatedly up and down, what you’re doing is rearranging all the magnetic “cows” (domains) inside so they point the same way.

Phew, we got to the end! If you want to learn more about magnets you should probably study “electromagnetism” at university 😀