magnetismu

Magnetism refers to a class of physical phenomena associated with magnetic fields and the forces they exert on matter. Magnetic effects arise mainly from moving electric charges and from intrinsic magnetic moments of elementary particles, notably electrons. In classical terms, magnetic fields are described by the vector field B and the related quantities H and M, with magnetization M describing how a material responds to the field. The field can exert torques on magnetic dipoles and produce attractive or repulsive interactions between magnets and magnetic materials. Maxwell’s equations govern the behavior of magnetic fields and their coupling to electricity.

There are several distinct kinds of magnetism. Ferromagnetism features a strong, spontaneous alignment of magnetic moments, producing permanent magnets as seen in iron, nickel, and cobalt. Paramagnetism involves weak attraction to a magnetic field due to unpaired electrons, with a susceptibility that typically decreases with temperature. Diamagnetism is a weak repulsion caused by induced currents opposing the applied field and is present in all materials, though often masked by stronger effects. More complex forms include antiferromagnetism, where neighboring moments align oppositely resulting in little net magnetization, and ferrimagnetism, where opposing moments do not cancel completely.

Earth’s magnetism is a geophysical phenomenon generated by convecting liquid iron in the outer core, producing the geomagnetic field that protects the planet from solar radiation and guides navigation. Technologies relying on magnetism include electric machines (motors and generators), magnetic data storage, magnetic sensing, and medical imaging techniques such as magnetic resonance imaging. Magnetic measurements use units such as tesla for magnetic flux density and the ampere per meter for magnetization, with material properties often described by magnetic susceptibility.