elektromagnetism

Electromagnetism is a branch of physics that studies the interactions between electric charges and currents and the associated magnetic fields. It describes how electric and magnetic fields propagate, interact with matter, and give rise to light and other electromagnetic phenomena. The theory unifies electricity, magnetism, and optics into a single framework.

The modern foundation is Maxwell's equations, a set of four relations between electric fields, magnetic fields, charges, and currents. Gauss's law connects electric fields to charge distribution; Gauss's law for magnetism states there are no magnetic monopoles; Faraday's law describes how a changing magnetic field induces an electric field; the Ampere-Maxwell law links magnetic fields to currents and to changing electric fields via displacement current. Together, these equations predict that changing electric and magnetic fields can sustain electromagnetic waves that propagate through space at the speed of light, c = 1/√(ε0 μ0).

Electromagnetic waves span a broad spectrum from radio waves to gamma rays. They can interact with matter through processes such as absorption, reflection, refraction, scattering, and polarization. Light is a portion of this spectrum visible to the human eye, while other portions have diverse applications in communications, medicine, and industry.

Historically, the subject drew on experiments by Ørsted, Faraday, and Ampère, culminating in Maxwell's synthesis in the 1860s. In quantum theory, electromagnetic interactions are described by quantum electrodynamics, with photons as the quanta of the field. Today, electromagnetism underpins technologies such as power generation and distribution, motors, wireless communication, optical fibers, imaging, and spectroscopy.