Poynting Vector

(redirected from Poynting flux)

Poynting vector

[′pȯint·iŋ ‚vek·tər]
A vector, equal to the cross product of the electric-field strength and the magnetic-field strength (mks units) whose outward normal component, when integrated over a closed surface, gives the outward flow of electromagnetic energy through that surface.

Poynting Vector


the vector of the flux density of electromagnetic energy; named after the English physicist J. H. Poynting (1852–1914).

The magnitude of the Poynting vector is equal to the energy transferred per unit time through a unit of surface perpendicular to the direction of propagation of the electromagnetic energy, that is, to the direction of the Poynting vector. In the absolute (Gaussian) system of units, Π = (e/π)[EH], where [EH] is the vector product of the intensities of the electric flux E and magnetic field H and c is the speed of light in a vacuum; in the International System, Π = [EH]. The flow of the Poynting vector through a closed surface bounding a system of charged particles gives the value of the energy lost by the system per unit time as a result of the emission of electromagnetic waves. The momentum density of an electromagnetic field g is expressed in terms of the Poynting vector: