Editing Poynting vector (section)

{{Short description|Measure of directional electromagnetic energy flux}}
[[File:DipoleRadiation.gif|300px|thumb|[[Dipole radiation]] of a dipole vertically in the page showing electric field strength (color) and Poynting vector (arrows) in the plane of the page.]]
{{Electromagnetism|Electrodynamics}}

In [[physics]], the '''Poynting vector''' (or '''Umov–Poynting vector''') represents the directional [[energy flux]] (the energy transfer per unit area, per unit time) or ''[[power (physics)|power flow]]'' of an [[electromagnetic field]]. The [[SI]] unit of the Poynting vector is the [[watt]] per square metre (W/m<sup>2</sup>); kg/s<sup>3</sup> in [[SI base unit]]s. It is named after its discoverer [[John Henry Poynting]] who first derived it in 1884.<ref name="Stratton1941">{{cite book
| last = Stratton
| first = Julius Adams | author-link = Julius Adams Stratton
| title = Electromagnetic Theory
| edition = 1st
| publisher = McGraw-Hill
| place = New York
| year = 1941
| isbn = 978-0-470-13153-4
| url = https://books.google.com/books?id=zFeWdS2luE4C
}}</ref>{{rp|p=132}}  [[Nikolay Umov]] is also credited with formulating the concept.<ref>{{cite web | title=Пойнтинга вектор | website=Физическая энциклопедия | url=http://femto.com.ua/articles/part_2/2938.html | language=ru | access-date=2022-02-21}}</ref> [[Oliver Heaviside]] also discovered it independently in the more general form that recognises the freedom of adding the [[curl (mathematics)|curl]] of an arbitrary vector field to the definition.<ref name="Nahin2002">{{cite book | isbn=9780801869099 | year=2002 | title=Oliver Heaviside: The Life, Work, and Times of an Electrical Genius of the Victorian Age | last=Nahin | first=Paul J. | author-link=Paul J. Nahin |page=131| publisher=JHU Press }}</ref>  The Poynting vector is used throughout [[electromagnetics]] in conjunction with [[Poynting's theorem]], the [[continuity equation]] expressing [[conservation of energy|conservation of electromagnetic energy]], to calculate the power flow in electromagnetic fields.