Editing Electromagnetic field (section)

== History ==
{{main|History of electromagnetic theory}}
[[File:Results of Michael Faraday's iron filings experiment. Wellcome M0000164.jpg|thumb|Results of Michael Faraday's iron filings experiment.]]
The empirical investigation of electromagnetism is at least as old as the ancient Greek philosopher, mathematician and scientist [[Thales of Miletus]], who around 600&nbsp;BCE described his experiments rubbing fur of animals on various materials such as amber creating static electricity.{{sfnp|ps=|ThoughtCo|2018}} By the 18th century, it was understood that objects can carry positive or negative [[electric charge]], that two objects carrying charge of the same sign repel each other, that two objects carrying charges of opposite sign attract one another, and that the strength of this force falls off as the square of the distance between them. [[Michael Faraday]] visualized this in terms of the charges interacting via the [[electric field]]. An electric field is produced when the charge is stationary with respect to an observer measuring the properties of the charge, and a [[magnetic field]] as well as an electric field are produced when the charge moves, creating an electric current with respect to this observer. Over time, it was realized that the electric and magnetic fields are better thought of as two parts of a greater whole—the electromagnetic field. In 1820, [[Hans Christian Ørsted]] showed that an electric current can deflect a nearby compass needle, establishing that electricity and magnetism are closely related phenomena.{{sfnp|ps=|Stauffer|1957}} Faraday then made the seminal observation that time-varying magnetic fields could induce electric currents in 1831. 

In 1861, [[James Clerk Maxwell]] synthesized all the work to date on electrical and magnetic phenomena into a single mathematical theory, from which he then deduced that [[light]] is an electromagnetic wave. Maxwell's continuous field theory was very successful until evidence supporting the atomic model of matter emerged. Beginning in 1877, [[Hendrik Lorentz]] developed an atomic model of electromagnetism and in 1897 [[J. J. Thomson]] completed experiments that defined the [[electron]]. The Lorentz theory works for free charges in electromagnetic fields, but fails to predict the energy spectrum for bound charges in atoms and molecules. For that problem, [[quantum mechanics]] is needed, ultimately leading to the theory of [[quantum electrodynamics]].

Practical applications of the new understanding of electromagnetic fields emerged in the late 1800s. The electrical generator and motor were invented using only the empirical findings like Faraday's and Ampere's laws combined with practical experience.