How Ordinary Iron Becomes Magnetic—and How to Make or Break a Magnet

When a piece of iron is placed near a magnet, it becomes a temporary magnet due to magnetic induction. This means the iron's atoms align in such a way that the end near the magnet's north pole becomes a south pole, and vice versa, causing attraction. Magnetic induction happens because the magnetic field from the magnet forces the tiny magnetic domains inside the iron to line up in the same direction, making the iron act like a magnet as long as it stays close to the real magnet. For example, if you bring an iron nail near a bar magnet, the nail can pick up small iron pins because it has become temporarily magnetised. In real life, this is why iron objects like keys or paperclips can stick to a magnet even if they were not magnetic before. Many students think the iron becomes a permanent magnet, but it actually loses its magnetism once the real magnet is removed.

You can make a magnet from an iron bar using the single touch or double touch methods. In the single touch method, a bar magnet is stroked along the length of the iron bar from one end to the other, always in the same direction, and then lifted away before repeating. The end where the stroke finishes becomes the opposite pole of the magnet used. In the double touch method, two bar magnets are placed with their opposite poles near the centre of the iron bar. They are moved together from the centre to the ends, then lifted and brought back to the centre, repeating this process several times. The ends of the iron bar where the magnets leave become opposite poles to the magnets used. For example, if you stroke an iron bar with the north pole of a magnet from left to right, the right end becomes a south pole. A common mistake is to rub the bar back and forth, which cancels out the magnetising effect instead of strengthening it.

An electromagnet is made by winding insulated copper wire around an iron bar and passing an electric current through the wire. The electric current creates a magnetic field, turning the iron bar into a magnet as long as the current flows. The strength of an electromagnet can be increased by increasing the number of turns of the wire or by increasing the current. Electromagnets are widely used because they can be switched on and off. For example, they are used in electric bells and cranes for lifting scrap iron. In real life, the doorbell in many homes uses an electromagnet to move a hammer that strikes the bell. Some students confuse electromagnets with permanent magnets, but electromagnets lose their magnetism when the current stops.

A magnet can be demagnetised by heating it, hammering or rough handling, or by keeping like poles together. Heating causes the magnetic domains to lose alignment, hammering or dropping shakes the domains out of order, and storing like poles together cancels out their magnetism. To store magnets safely, they should be kept in pairs with unlike poles adjacent, separated by soft iron keepers, which help preserve their magnetism. For example, two bar magnets are placed side by side with a soft iron strip connecting their opposite poles. In real life, if you drop a magnet repeatedly, it may lose its strength. Many students forget that storing magnets with like poles together weakens them instead of preserving them.