magnet

A magnet is a body from which a magnetic field emanates. It has two magnetic poles, the north and south pole, over which the magnetic field lines run inside and outside the magnet. Inside the magnet, the magnetic field lines run in the magnet body, namely from the south pole to the north pole, outside they run through the medium surrounding the magnet, usually air, from the north pole to the south pole.

The magnetic field surrounding the magnet is determined by its direction and its magnetic field strength. The magnetic force underlying the magnetic fields finds its cause in magnetism.

Magnet with north and south pole and the course of the magnetic field lines

Magnets are divided into permanent magnets and electromagnets. Permanent magnets consist of magnetic materials that permanently generate magnetic fields. These include hard magnetic materials with high coercive force and remanence. This makes the magnets insensitive to external fields. Hard magnetic materials include hardened steels and alloys. Soft magnetic materials behave differently. They are used where constant remagnetization is required. Soft magnetic materials include iron, nickel and cobalt. The permeability of soft magnetic materials is much greater than 1.

Electromagnets consist of soft magnetic materials surrounded by a coil. The magnetic field generated by the coil passes through the soft iron core and shows its effect in mechanical power transmission. Examples are measuring devices, motors, generators, lifting solenoids, relays and many more.