Conservation Laws, Electrodynamics, Poynting Vector, Poynting Theorem, Physics.
charge density ρ. This leads us to the following expression: dW = ρ (E.v) dV dt = (E.J) dV dt Multiplying the charge density with the velocity simply gives us the current density. Differentiate the above equation with respect to time and it will be immediately evident that the dot product on the