Magnezie

Magnezie is a term used in some languages to denote magnetism—the study of magnetic phenomena that arise from magnetic dipoles and moving electric charges. In physics, magnetism describes the forces and fields produced by magnets, current-carrying conductors, and electrons' intrinsic spin. Magnetic effects include attraction or repulsion between magnets, the interaction of magnetic materials with external fields, and the generation of magnetic fields themselves.

Magnetic fields are described by the magnetic field B and are governed by Maxwell's equations, including Gauss's law for magnetism, which states that the net magnetic flux through a closed surface is zero, and Ampère's law with Maxwell's addition, which relates changing electric fields and currents to magnetic fields. The theory unifies with electricity in the framework of electromagnetism, explaining how moving charges produce magnetic effects and how changing magnetic fields induce electric currents.

Materials exhibit different magnetic orders, such as diamagnetism, paramagnetism, and ferromagnetism. Ferromagnetic materials consist of magnetic domains that align under external fields, producing hysteresis and saturation. Key concepts include Curie temperature, which marks a transition to or from magnetic order, and coercivity, which measures resistance to demagnetization.

Historically, magnetism has roots in observations of lodestones and compass needles, with significant milestones from William Gilbert, Hans Christian Ørsted, Michael Faraday, André-Marie Ampère, and James Clerk Maxwell, who unified electricity and magnetism into a single theory.

Applications of magnetism include navigation with compasses, electrical machines such as motors and generators, data storage in magnetic media, magnetic resonance imaging (MRI) in medicine, and various sensing and actuation technologies. From a quantum perspective, magnetism arises in part from electron spin and orbital motion, with exchange interactions leading to collective magnetic order in materials. In some languages, magnezie is the standard term for magnetism; in English, magnetism is used.