Why Do Magnets Always Point North and South?

A material is magnetic if it is attracted to a magnet, and non-magnetic if it is not. To test if something is magnetic, simply bring a magnet close to it and see if there is any attraction. Materials like iron, nickel, and cobalt are magnetic, while materials like wood, plastic, glass, and rubber are non-magnetic. Magnetite, also called lodestone, is a natural magnet found in nature. Most magnets we use daily, such as bar magnets, horseshoe magnets, ring magnets, and cylindrical magnets, are artificial and made in factories. For example, if you bring a magnet near an iron nail, it will stick to the magnet, but a plastic pen will not. In real life, fridge doors use magnetic strips to keep them closed, while wooden doors do not. Some students think all metals are magnetic, but only a few metals like iron, nickel, and cobalt are actually attracted to magnets.

The two ends of a magnet, where its force is strongest, are called its poles—these are the north pole and the south pole. You can find the poles by sprinkling iron filings around a magnet placed on a sheet of paper; the filings gather most densely at the ends, showing the poles. When two magnets are brought close, like poles (north-north or south-south) repel each other, while unlike poles (north-south) attract each other. For example, if you try to push the north ends of two bar magnets together, they push away from each other, but if you bring a north end near a south end, they stick together. In real life, magnetic compasses use this property to help us find direction. Many students think the middle of a magnet is the strongest, but the poles are actually where the magnetic force is greatest.

A freely suspended bar magnet always comes to rest in the north–south direction because Earth's magnetic field causes one end to point north and the other to point south. This property is used in magnetic compasses, where a small magnet needle is balanced and can rotate freely; the needle aligns itself along the north–south direction, helping us find directions. For example, if you tie a thread around the middle of a bar magnet and hang it freely, it will settle so that one end points towards the geographic north and the other towards the south. In real life, travelers and sailors use compasses to navigate. Some students confuse the geographic north with the magnetic north, but the compass points to the magnetic north, which is close to, but not exactly at, the geographic north.

You can make a magnet from an iron object by stroking it with one pole of a bar magnet in one direction several times. This is called the stroking method. After a while, the iron object becomes magnetized and can attract other iron objects. Magnets should be stored with keepers—pieces of soft iron placed across their poles—to prevent them from losing their magnetism. Bar magnets are usually stored in pairs with their opposite poles joined by keepers. For example, if you stroke an iron nail with the north pole of a bar magnet from one end to the other, always in the same direction, the nail will become a magnet. In real life, if magnets are dropped or heated, they can lose their magnetism. Many students think magnets last forever, but careless handling can make them weak or demagnetize them.