Definition
In Poynting's original paper and in many textbooks, it is usually denoted by S or N, and defined as:
which is often called the Abraham form; where E is the electric field and H the magnetic field. (All bold letters represent vectors.)
Occasionally an alternative definition in terms of electric field E and the magnetic flux density B is used. It is even possible to combine the displacement field D with the magnetic flux density B to get the Minkowski form of the Poynting vector, or use D and H to construct another. The choice has been controversial: Pfeifer et al. summarize the century-long dispute between proponents of the Abraham and Minkowski forms.
The Poynting vector represents the particular case of an energy flux vector for electromagnetic energy. However, any type of energy has its direction of movement in space, as well as its density, so energy flux vectors can be defined for other types of energy as well, e.g., for mechanical energy. The Umov-Poynting vector discovered by Nikolay Umov in 1874 describes energy flux in liquid and elastic media in a completely generalized view.
Read more about this topic: Poynting Vector
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