It is possible to derive alternative versions of Poynting's theorem.

This practically limits Poynting's theorem in this form to fields in vacuum.

Using the divergence theorem, Poynting's theorem can be rewritten in integral form:

The more general case is described by Poynting's theorem above, where it occurs as a divergence, which means that it can only describe the change of energy density in space, rather than the flow.

In electrodynamics, Poynting's theorem is a statement of energy conservation for the electromagnetic field, in the form of a partial differential equation, due to the British physicist John Henry Poynting.

Poynting's theorem is analogous to the work-energy theorem in classical mechanics, and mathematically similar to the continuity equation, because it relates the energy stored in the electromagnetic field to the work done on a charge distribution (i.e. an electrically charged object), through energy flux.

It is possible to derive alternative versions of Poynting's theorem.

This practically limits Poynting's theorem in this form to fields in vacuum.

Using the divergence theorem, Poynting's theorem can be rewritten in integral form:

The more general case is described by Poynting's theorem above, where it occurs as a divergence, which means that it can only describe the change of energy density in space, rather than the flow.

In electrodynamics, Poynting's theorem is a statement of energy conservation for the electromagnetic field, in the form of a partial differential equation, due to the British physicist John Henry Poynting.

Poynting's theorem is analogous to the work-energy theorem in classical mechanics, and mathematically similar to the continuity equation, because it relates the energy stored in the electromagnetic field to the work done on a charge distribution (i.e. an electrically charged object), through energy flux.