Magnetens

Magnets are objects that generate magnetic fields, producing forces on other magnets and on certain materials, most notably iron. They have north and south poles, and the field lines leave from the north pole and enter the south. In ferromagnetic materials, microscopic magnetic moments can align to produce a strong net magnetization.

There are two broad classes: permanent magnets, which retain magnetization without power, and electromagnets, which produce a magnetic field when electric current flows. Permanent magnets use materials such as ferrites, alnico, neodymium-iron-boron, and samarium-cobalt. Electromagnets rely on coils of wire around a ferromagnetic core and can be switched off.

Key parameters describe magnet performance: remanence, coercivity, and energy product. Temperature affects magnetism; the Curie temperature is the point above which many permanent magnets lose their magnetization. Magnetic domains—small regions where moments align—collectively determine a material’s level of magnetization and how easily it can be demagnetized.

Common applications include electric motors and generators, transformers, loudspeakers, magnetic storage devices, and medical imaging (MRI). Magnets also enable sensors, magnetic separation, and actuators. Safety concerns include strong attraction of objects, risk of injury, and interference with medical implants; magnets should be kept away from sensitive electronics and heat sources.

The study of magnetism traces back to lodestones used in ancient civilizations. Developments in the 19th century established the relation between electricity and magnetism, leading to modern magnet technology. Today, rare-earth magnets provide high strength and are widely used in technology and industry.