Electromagnetism

In physics, electromagnetism is an interaction that occurs between <a href="/facts/Particles/JHKr2w6h">particles</a> with <a href="/facts/Electric_charge/xxsBfmlB">electric charge</a> via <a href="/facts/Electromagnetic_fields/MacraS8y">electromagnetic fields</a>. The electromagnetic force is one of the four <a href="/facts/Fundamental_forces/WrFEJaFl">fundamental forces</a> of nature. It is the dominant force in the interactions of <a href="/facts/Atoms/FoQ4kGN5">atoms</a> and <a href="/facts/Molecules/N9ljSfFq">molecules</a>. Electromagnetism can be thought of as a combination of <a href="/facts/Electrostatics/bxkuW6s4">electrostatics</a> and <a href="/facts/Magnetism/eo75vApl">magnetism</a>, which are distinct but closely intertwined phenomena. Electromagnetic forces occur between any two charged particles. Electric forces cause an attraction between particles with opposite charges and repulsion between particles with the same charge, while magnetism is an interaction that occurs between charged particles in relative motion. These two forces are described in terms of electromagnetic fields. Macroscopic charged objects are described in terms of <a href="/facts/Coulomb%2527s_law/V0lR5NKv">Coulomb's law</a> for electricity and <a href="/facts/Amp%25C3%25A8re%2527s_force_law/7NMvLnc8">Ampère's force law</a> for magnetism; the <a href="/facts/Lorentz_force/aq1Rc3SS">Lorentz force</a> describes microscopic charged particles.
The electromagnetic force is responsible for many of the <a href="/facts/Chemistry/SrNqkGVm">chemical</a> and physical phenomena observed in daily life. The electrostatic attraction between <a href="/facts/Atomic_nuclei/orpIm5Xl">atomic nuclei</a> and their <a href="/facts/Electron/L0KBo5cW">electrons</a> holds atoms together. Electric forces also allow different atoms to combine into molecules, including the <a href="/facts/Macromolecule/039ULSLg">macromolecules</a> such as <a href="/facts/Proteins/Jxmagu3E">proteins</a> that form the basis of <a href="/facts/Life/DNw7NUId">life</a>. Meanwhile, magnetic interactions between the <a href="/facts/Electron_magnetic_moment/guAK2JJ2">spin</a> and <a href="/facts/Azimuthal_quantum_number/vHSIzbFC">angular momentum</a> magnetic moments of electrons also play a role in chemical reactivity; such relationships are studied in <a href="/facts/Spin_chemistry/e2CPtKn2">spin chemistry</a>. Electromagnetism also plays several crucial roles in modern <a href="/facts/Technology/9Uav5WVR">technology</a>: electrical energy production, transformation and distribution; light, heat, and sound production and detection; fiber optic and wireless communication; sensors; computation; electrolysis; electroplating; and mechanical motors and actuators.
Electromagnetism has been studied since ancient times. Many ancient civilizations, including the <a href="/facts/Ancient_Greece/PTVBrWXq">Greeks</a> and the <a href="/facts/Maya_civilization/JMynpRSR">Mayans</a>, created wide-ranging theories to explain <a href="/facts/Lightning/dLTuxz8n">lightning</a>, <a href="/facts/Static_electricity/tkGDkl7f">static electricity</a>, and the attraction between magnetized pieces of <a href="/facts/Iron_ore/rQMEvgMh">iron ore</a>. However, it was not until the late 18th century that scientists began to develop a mathematical basis for understanding the nature of electromagnetic interactions. In the 18th and 19th centuries, prominent scientists and mathematicians such as <a href="/facts/Charles-Augustin_de_Coulomb/T4EEdFIq">Coulomb</a>, <a href="/facts/Gauss/f4eSMBD7">Gauss</a> and <a href="/facts/Faraday/NDcc3lyt">Faraday</a> developed namesake laws which helped to explain the formation and interaction of electromagnetic fields. This process culminated in the 1860s with the discovery of <a href="/facts/Maxwell%2527s_equations/LfJ1drHS">Maxwell's equations</a>, a set of four <a href="/facts/Partial_differential_equation/DyPsBlv7">partial differential equations</a> which provide a complete description of classical electromagnetic fields. Maxwell's equations provided a sound mathematical basis for the relationships between electricity and magnetism that scientists had been exploring for centuries, and predicted the existence of self-sustaining <a href="/facts/Electromagnetic_waves/Ynx7ujCW">electromagnetic waves</a>. Maxwell postulated that such waves make up <a href="/facts/Visible_light/jeofpMn4">visible light</a>, which was later shown to be true. Gamma-rays, x-rays, ultraviolet, visible, infrared radiation, microwaves and radio waves were all determined to be electromagnetic radiation differing only in their range of frequencies.
In the modern era, scientists continue to refine the theory of electromagnetism to account for the effects of <a href="/facts/Modern_physics/J9Kko1qU">modern physics</a>, including <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum mechanics</a> and <a href="/facts/Theory_of_relativity/qGHj3eTC">relativity</a>. The theoretical implications of electromagnetism, particularly the requirement that observations remain consistent when viewed from various moving frames of reference (<a href="/facts/Relativistic_electromagnetism/MqKhJPy2">relativistic electromagnetism</a>) and the establishment of the speed of light based on properties of the medium of propagation (<a href="/facts/Permeability_(electromagnetism)/GA7CcRLU">permeability</a> and <a href="/facts/Permittivity/Sd3WtgT1">permittivity</a>), helped inspire <a href="/facts/Albert_Einstein/CNTet8qu">Einstein's</a> theory of <a href="/facts/Special_relativity/vsFFc63E">special relativity</a> in 1905. <a href="/facts/Quantum_electrodynamics/zPteAr6G">Quantum electrodynamics</a> (QED) modifies Maxwell's equations to be consistent with the <a href="/facts/Quantization_(physics)/fvs2Jwpn">quantized</a> nature of matter. In QED, changes in the electromagnetic field are expressed in terms of discrete excitations, particles known as <a href="/facts/Photons/mFNhAEzA">photons</a>, the <a href="/facts/Quantum/4x5QTxGB">quanta</a> of light.

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Electromagnetism