## Poynting's theorem |

This article may be . (October 2017) ( |

This article needs attention from an expert in Physics. (October 2017) |

In **Poynting's theorem** is a statement of ^{[clarification needed]} in the form of a ^{[1]} Poynting's theorem is analogous to the

- statement
- derivation
- poynting vector in macroscopic media
- alternative forms
- generalization
- notes
- external links

In words, the theorem is an energy balance:

*The***rate of energy transfer (per unit volume)**from a region of space equals the**rate of**on a charge distribution plus thework doneleaving that region.energy flux

A second statement can also explain the theorem - "The decrease in the electromagnetic energy per unit time in a certain volume is equal to the sum of work done by the field forces and the net outward flux per unit time".

Mathematically, this is summarised in **differential form** as:

where ∇•**S** is the **J**•**E** is the rate at which the fields do work on a charged object (**J** is the **E** is the *u* is given by:^{[2]}

in which **B** is the **integral form**:

where is the boundary of a volume *V*. The shape of the volume is arbitrary but fixed for the calculation.

In *u* expanded in the following way, which resembles the

where

*ε*_{0}is theelectric constant and*μ*_{0}is themagnetic constant .- is the density of
reactive power driving the build-up of electric field, - is the density of
reactive power driving the build-up of magnetic field, and - is the density of
electric power dissipated by theLorentz force acting on charge carriers.

Other Languages

беларуская: Тэарэма Пойнтынга

Deutsch: Satz von Poynting

español: Teorema de Poynting

Esperanto: Teoremo de Poynting

فارسی: قضیه پوئینتینگ

français: Théorème de Poynting

հայերեն: Պոյնտինգի թեորեմ

हिन्दी: प्वाइन्टिंग प्रमेय

italiano: Teorema di Poynting

עברית: משפט פוינטינג

polski: Twierdzenie Poyntinga

português: Teorema de Poynting

русский: Теорема Пойнтинга

српски / srpski: Поинтингова теорема

українська: Теорема Пойнтінга

Tiếng Việt: Định lý Poynting

中文: 坡印亭定理