A permanent magnet never needs power, yet it always has a field. Inside its iron are countless tiny magnetic regions called domains — and the secret is simply that they are all pointing the same way.
A permanent magnet is a material that keeps its magnetism without any power supply. Its behaviour comes from the way its atoms are arranged: inside the iron, atoms group into tiny regions called domains, and each domain acts like a small magnet with its own north and south. What makes a permanent magnet special is that its domains are all lined up.
It answers the obvious question — why does a magnet stay magnetic when an electromagnet needs a current? The answer is that in a permanent magnet the alignment is locked in by the material itself. Nothing has to hold the domains in line, so the field persists. It also explains why a magnet can be weakened: shocking or heating it knocks the domains back out of alignment.
The bar runs across the middle with small arrows inside it: those are the domains, all pointing the same way, from the south end toward the north end. The curved blue lines outside are the field lines, running from the north pole round to the south pole. Below, a small box shows a piece of ordinary unmagnetised iron, where the domains point at random and cancel out.
Inside any magnetic material, the atoms group into regions called domains. Each domain is small, but it behaves like a complete little magnet, with a north end and a south end of its own. A single magnet contains an enormous number of them.
In a permanent magnet all these domains point the same way. That is the whole difference: instead of facing every which way, they agree. Aligning them does not create new magnetism; it simply lets the magnetism that was already there work together instead of cancelling.
Because the domains point the same way, their tiny fields reinforce one another. Add millions of them together and the result is a strong field around the whole bar — the field we see as the magnet's magnetism. The material's alignment being locked in is what keeps that field there without any power.
With the domains pointing from the south end toward the north end, the field emerges at the north pole. The field lines curve through the surrounding space and re-enter at the south pole, closing into loops. A magnet always has both poles; cutting it in half just makes two smaller magnets.
An ordinary piece of iron also contains domains, but they point in every possible direction, so their fields cancel and the iron shows no magnetism. Align those same domains — with a strong field or by making the material as a magnet — and the iron becomes magnetic. That is why a magnet can pick up a paper clip and magnetise it.
A magnetic domain is a tiny region inside a magnetic material where all the atoms' magnetic effects point the same way. Each domain behaves like a small magnet of its own, with its own north and south end.
Because its domains are locked in alignment. In ordinary iron the domains point in random directions and cancel out, but once they are lined up they all reinforce one another, so the material keeps a strong overall field.
An electromagnet needs a current to keep its field, because the coil's field is what holds the domains in line. In a permanent magnet the aligned domains stay put on their own, so the magnetism lasts without any power.
Yes. Heating it strongly or hitting it hard can shake the domains back out of alignment, and then the magnetism weakens or disappears. The alignment is fixed but not indestructible.
It is a contrast. An ordinary piece of iron also has domains, but they point in every direction, so their fields cancel and the iron shows no magnetism. Comparing the two shows that aligning the domains is what creates the magnet.