13 Facts About Poynting vector

In physics, the Poynting vector represents the directional energy flux or power flow of an electromagnetic field.

The Poynting vector is used throughout electromagnetics in conjunction with Poynting's theorem, the continuity equation expressing conservation of electromagnetic energy, to calculate the power flow in electromagnetic fields.

Poynting vector represents the particular case of an energy flux vector for electromagnetic energy.

The Umov–Poynting vector discovered by Nikolay Umov in 1874 describes energy flux in liquid and elastic media in a completely generalized view.

Poynting vector appears in Poynting's theorem, an energy-conservation law:.

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One consequence of the Poynting vector formula is that for electromagnetic field to do work, both magnetic and electric fields must be present.

The instantaneous Poynting vector, given by the cross product of E and H will then be in the positive Z direction:.

Two alternative definitions of the Poynting vector are equal in vacuum or in non-magnetic materials, where.

Above form for the Poynting vector represents the instantaneous power flow due to instantaneous electric and magnetic fields.

Once the Poynting vector enters the conductor, it is bent to a direction that is almost perpendicular to the surface.

Inside the conductor, the Poynting vector represents energy flow from the electromagnetic field into the wire, producing resistive Joule heating in the wire.

Poynting vector occurs in Poynting's theorem only through its divergence, that is, it is only required that the surface integral of the Poynting vector around a closed surface describe the net flow of electromagnetic energy into or out of the enclosed volume.

However even though the Poynting vector was originally formulated only for the sake of Poynting's theorem in which only its divergence appears, it turns out that the above choice of its form is unique.