North poleHang a magnet so it can swing and this end points north. Its full name is the north-seeking pole.
South poleThe south-seeking pole, which cannot be cut away from the north pole. Break a magnet and each piece has both.
Horseshoe magnetBoth poles are close together. That makes the field between them concentrated and strong.
KeeperLeft across the poles, it helps the magnet keep its strength.
Its field 2
Magnetic field linesThey picture the magnetic field. The arrows give its direction, and the field is strongest where the lines are closest together.
Compass needleIts north end points the way the field runs. So small compasses are used to map the field round a magnet.
Inside the iron 2
Magnetic domainsEach acts like a tiny bar magnet. In iron that is not a magnet they point every which way, so they cancel each other out.
Aligned domainsPut iron in a magnetic field and its domains line up. Their fields add together, and the iron is a magnet.
How this list was compiled: Every name and fact checked on 2026-09-30, a name kept only where two independent sources use it. (1) OpenStax, College Physics 2e: 22.1 Magnets, https://openstax.org/books/college-physics-2e/pages/22-1-magnets; 22.2 Ferromagnets and Electromagnets, https://openstax.org/books/college-physics-2e/pages/22-2-ferromagnets-and-electromagnets; 22.3 Magnetic Fields and Magnetic Field Lines, https://openstax.org/books/college-physics-2e/pages/22-3-magnetic-fields-and-magnetic-field-lines (north and south poles, poles always in pairs, like poles repel, field lines and their direction from a compass needle, closeness of lines and strength, domains). (2) National High Magnetic Field Laboratory, Magnets from Mini to Mighty, https://nationalmaglab.org/magnet-academy/read-science-stories/science-simplified/magnets-from-mini-to-mighty/ (poles, field lines point away from a north pole and toward a south pole, domains lining up). (3) Wikipedia, text only: Magnet, Horseshoe magnet, Magnet keeper, Magnetic domain. (4) For the keeper and the horseshoe magnet also Millikan and Gale, A First Course in Physics (1913), https://archive.org/details/firstcourseinphy00millrich (a bar of soft iron, a keeper, placed across the poles; filings cling near the ends, the poles, and scarcely at all near the middle). Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
A bar magnet with its two poles and its field, a horseshoe magnet with its keeper, and the domains inside the iron. The poles carry no letters: the arrows tell you which is which.
Read the full guide
Follow the arrows
Field lines leave the north pole, loop round and go back in at the south pole, so the end the arrows point away from is north. The compass needle on the top line points the same way as the field there. A horseshoe magnet is a magnet bent so that its poles sit side by side; the keeper is the iron bar laid across them, which helps it keep its strength. The last view is inside the iron: its domains point every way until it is magnetized, then line up.
Field lines never cross, and the closer together they are, the stronger the field.
Like poles repel and unlike poles attract.
Questions and answers
What are the strongest parts of a magnet?
The poles, at its two ends. The field lines crowd together there, and iron filings cling in tufts near the ends of a magnet but hardly at all near the middle.
What are the parts of a horseshoe magnet?
A north pole and a south pole at the two ends of the U, side by side, and the bend that joins them. A keeper, a bar of soft iron laid across the poles, helps the magnet keep its strength.
What happens if you cut a magnet in half?
You get two smaller magnets, each with its own north pole and south pole. Poles always come in pairs: a north pole has never been found without a south pole.
What is a magnetic domain?
A small region inside iron where the atoms are lined up, so that it acts like a tiny bar magnet. In ordinary iron the domains point in random directions; in a magnet they are lined up.