Asked by andrew

define electromagnetism

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Answered by GPT-5 mini AI
Electromagnetism is the branch of physics that studies electric and magnetic fields, how they are generated by electric charges and currents, how they interact with charged particles, and how they propagate as electromagnetic waves. It unifies electric and magnetic phenomena into a single theory and describes one of the four fundamental forces of nature: the electromagnetic force.

Key points
- Fields and sources: Electric fields (E) arise from electric charges; magnetic fields (B) arise from moving charges (currents) and changing electric fields.
- Fundamental laws: In classical form, Maxwell's equations (plus the Lorentz force law) govern electromagnetism. The Lorentz force on a charge q moving with velocity v is F = q(E + v × B).
- Waves and light: Time-varying electric and magnetic fields propagate together as electromagnetic waves (radio waves, visible light, X-rays), which travel at the speed of light c in vacuum.
- Quantum view: In quantum electrodynamics (QED), electromagnetism is mediated by photons, the quanta of the electromagnetic field.
- Importance: Electromagnetism underlies electricity, magnetism, electronics, optics, communications, and much of modern technology.

Units and typical quantities: electric field E (volts per meter, V/m), magnetic flux density B (tesla, T), electric charge (coulomb, C).