Introduction to electromagnetism

<p>Electromagnetism is one of the <a href="/facts/Fundamental_interaction/WrFEJaFl">fundamental forces</a> of nature.  Early on, <a href="/facts/Electricity/hNC8D65W">electricity</a> and <a href="/facts/Magnetism/eo75vApl">magnetism</a> were studied separately and regarded as separate phenomena.  <a href="/facts/Hans_Christian_%C3%98rsted/qjmmHgIy">Hans Christian Ørsted</a> discovered that the two were related – <a href="/facts/Electric_current/Dc1xdnUX">electric currents</a> give rise to magnetism.  <a href="/facts/Michael_Faraday/NDcc3lyt">Michael Faraday</a> discovered the converse, that magnetism could <a href="/facts/Electromagnetic_induction/T36JjtgY">induce</a> electric currents, and <a href="/facts/James_Clerk_Maxwell/jtYyze61">James Clerk Maxwell</a> put the whole thing together in a unified theory of <a href="/facts/Electromagnetism/oAkmALHT">electromagnetism</a>.  <a href="/facts/Maxwell%27s_equations/LfJ1drHS">Maxwell's equations</a> further indicated that <a href="/facts/Electromagnetic_wave/Ynx7ujCW">electromagnetic waves</a> existed, and the experiments of <a href="/facts/Heinrich_Hertz/sbL2MSpM">Heinrich Hertz</a> confirmed this, making <a href="/facts/Radio/XFr909M2">radio</a> possible.  Maxwell also postulated, correctly, that <a href="/facts/Light/jeofpMn4">light</a> was a form of electromagnetic wave, thus making all of <a href="/facts/Optics/p0vq4S1T">optics</a> a branch of electromagnetism.  <a href="/facts/Radio_wave/XmB6WPpF">Radio waves</a> differ from light only in that the <a href="/facts/Wavelength/kcJU0ymz">wavelength</a> of the former is much longer than the latter.  <a href="/facts/Albert_Einstein/CNTet8qu">Albert Einstein</a> showed that the <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a> arises through the <a href="/facts/Classical_electromagnetism_and_special_relativity/0UEQ840t">relativistic motion</a> of the <a href="/facts/Electric_field/tt4MooBs">electric field</a> and thus magnetism is merely a side effect of electricity.  The modern theoretical treatment of electromagnetism is as a <a href="/facts/Quantum_field/VoewsNJV">quantum field</a> in <a href="/facts/Quantum_electrodynamics/zPteAr6G">quantum electrodynamics</a>.
</p><p>In many situations of interest to <a href="/facts/Electrical_engineering/YYXW1KLW">electrical engineering</a>, it is not necessary to apply quantum theory to get correct results.  <a href="/facts/Classical_physics/gGnINVPE">Classical physics</a> is still  an accurate approximation in most situations involving <a href="/facts/Macroscopic/NLwPDtLe">macroscopic</a> objects.  With few exceptions, quantum theory is only necessary at the <a href="/facts/Atomic_scale/fn1VssXt">atomic scale</a> and a simpler classical treatment can be applied.  Further simplifications of treatment are possible in limited situations.  <a href="/facts/Electrostatics/bxkuW6s4">Electrostatics</a> deals only with stationary <a href="/facts/Electric_charge/xxsBfmlB">electric charges</a> so magnetic fields do not arise and are not considered.  <a href="/facts/Permanent_magnet/vvrg6VSk">Permanent magnets</a> can be described without reference to electricity or electromagnetism.  <a href="/facts/Circuit_theory/IjmVqbG8">Circuit theory</a> deals with <a href="/facts/Electrical_network/zt94kTW0">electrical networks</a> where the fields are largely confined around current carrying <a href="/facts/Electrical_conductor/BSuyupLP">conductors</a>.  In such circuits, even Maxwell's equations can be dispensed with and simpler formulations used.  On the other hand, a quantum treatment of electromagnetism is important in <a href="/facts/Chemistry/SrNqkGVm">chemistry</a>.  <a href="/facts/Chemical_reaction/GpqWlKrz">Chemical reactions</a> and <a href="/facts/Chemical_bond/ArNUMnIB">chemical bonding</a> are the result of <a href="/facts/Quantum_mechanical/BRc3Mzgr">quantum mechanical</a> interactions of <a href="/facts/Electron/L0KBo5cW">electrons</a> around <a href="/facts/Atom/FoQ4kGN5">atoms</a>.  Quantum considerations are also necessary to explain the behaviour of many electronic devices, for instance the <a href="/facts/Tunnel_diode/BVtMxHzU">tunnel diode</a>.
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Introduction to electromagnetism open-in-new

Introduction to electromagnetism