Electromagnetism

Electromagnetism is the physics of the electromagnetic field, including its effect on electrically charged particles.

The electromagnetic field is a field, encompassing all of space, made up of the electric field and the magnetic field. The electric field is produced by stationary electric charges, and gives rise to the electric force, the force experienced in static electricity; it is also the force that drives the flow of current in electrical conductors (the phenomenon known as electricity.) The magnetic field is an additional field produced by moving charges, which gives rise to the magnetic force one associates with magnets.

While the electric and magnetic forces may sound fairly esoteric, almost all of the phenomena one encounters in daily life (with the exception of gravity) actually result from electromagnetism. The forces between atoms, including the attractive forces between atoms in a solid that give rise to the rigidity of solids, are predominently electromagnetic, arising from the positive electric charge of the protons in atomic nuclei and the negative electric charge of the electrons surrounding the nuclei. So are the forces acting on the electrons in atoms, whose behavior gives rise to the varied phenomena observed in chemical reactions. Finally, it turns out that light can be described as a set of travelling disturbances in the electromagnetic field (i.e. electromagnetic waves), so all optical phenomena are actually electromagnetic in nature

Theories of electromagnetism

The theory of classical electromagnetism was developed by various physicists over the course of the 19th century, culminating in the work of James Clerk Maxwell, who unified the preceding developments into a single theory and discovered the electromagnetic nature of light. Classical electromagnetism describes the behavior of the electromagnetic field using a set of equations known as Maxwell's equations. The force that the electromagnetic field exerts on electrically charged particles is described using the Lorentz force law.

Electrodynamics is a (somewhat poorly-defined) subfield of electromagnetism that deals with rapidly changing electric and magnetic fields, and their effects on the motion of charged particles.

The invention of quantum mechanics necessitated the invention of a quantum theory of electromagnetism. This theory, which was completed in the 1940s, is known as quantum electrodynamics.




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