An interpretation of the energy conservation law for a point charge moving in a uniform electric field
Moscow State Institute of Electronic Technology (Technical University), Zelenograd, Moscow, Russian Federation
The standard interpretation of the energy conservation law accepted in the theory of electromagnetism maintains
that a change in the field energy occurring in a volume is the sum
of the energy increment in the volume due to the Poynting vector
flow and the energy dissipated as heat in the interaction of
charge carriers with the medium in which these carriers move.
We show that the work done by an external electric field on a
moving point charge is due to two sources: the energy arriving at
the charge with the Poynting vector flow and a specific channel
of energy supply to the charge originating from the interaction
of the charge’s field with the external field. Interestingly, at
nonrelativistic charge velocities (v≪c), 2/3 of the energy is supplied by the Poynting vector flow and 1/3 by the second
channel. In the ultrarelativistic case (v≤c), all of the energy comes with the Poynting vector flow.