# Poynting vector

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In physics, the Poynting vector can be thought of as representing the energy flux (in W/m2) of an electromagnetic field. It is named after its inventor John Henry Poynting. Oliver Heaviside and Nikolay Umov independently co-invented the Poynting vector. In Poynting's original paper and in many textbooks it is defined as

which is often called the Abraham form; here E is the electric field and H the auxiliary magnetic field.[1][2] (All bold letters represent vectors.) Sometimes, an alternative definition in terms of electric field E and the magnetic field B is used, which is explained below. It is even possible to combine the displacement field D with the magnetic field B to get the Minkowski form of the Poynting vector, or use D and H to construct another.[3] The choice has been controversial: Pfeifer et al.[4] summarize the century-long dispute between proponents of the Abraham and Minkowski forms.

## Contents

### Interpretation

The Poynting vector appears in Poynting's theorem, an energy-conservation law,[2]

where Jf is the current density of free charges and u is the electromagnetic energy density,

where B is the magnetic field and D the electric displacement field.