A bar magnet is a rectangular object that has a magnetic field. It is usually made of iron or steel, but it can also be made of any ferromagnetic substance or a ferromagnetic composite. A bar magnet is almost always a permanent magnet, meaning that it will retain its magnetic field for a significant period of time without the use of a supplied electric current.

Each end of a bar magnet is considered a pole – one being north, the other south. When freely suspended, a bar magnet will align itself so that the end of its northern pole points towards the Earth’s magnetic North Pole. This works in the exact same manner as a compass needle, which itself uses or is a magnet. If a bar magnet has one end painted red, that end is traditionally the bar magnet’s north pole.

Bar magnets are usually made of ferromagnetic materials. Ferromagnetic materials are elements that can naturally have a magnetic field. They include cobalt, iron, and nickel. Some magnets are made of composite materials which combine ferromagnetic materials with other substances such as aluminum, clay, or resin.

A bar magnet, like other magnets, has uses based on its magnetic attraction. This magnetic attraction draws other ferromagnetic materials to it or the bar magnet towards them. These uses include: picking up small ferromagnetic items such as screws and metal shavings; being used as “magnetic stirring rods” on laboratory hotplates; and holding papers and other items to the sides of refrigerators.

Like other magnets, the magnetic field generated by a bar magnet can damage electronic equipment. A bar magnet placed near a hard drive, computer disk, or even a video cassette can cause the data stored by the magnetic particles on the item to be damaged. Bar magnets placed on the sides of speakers or other sound devices can cause disruptions in the sound or even permanent damage. A bar magnet placed on the side of a computer can result in the system being deactivated, and may even make it completely inoperable.

Bar magnets have been used for years to demonstrate magnetic fields and magnetic lines of force. One demonstration is to pour metal shavings (filings) onto a piece of paper that is suspended above a magnet. If done currently, over time the filings will align themselves into arcs going outward from the bar magnet’s north and south poles. Another demonstration involves attempt to touch the north poles of two different weak bar magnets together. The poles repel each-other. Still another demonstration involves cutting a bar magnet in half and seeing what happens. The cutting results in two bar magnets, though excessive force or heat can possibly demagnetize the bar instead.