I have a question regarding sources of electromagnetic potentials:
As far as I know, wave equations for the scalar and magnetic vector potentials can be derived from Maxwell equations employing the Lorenz gauge. If there are no charges then the wave equations are homogeneous. However in the presence of charges the wave equations are inhomogeneous and contain source terms. I haven't worked it out mathematically completely, but can't one show that charges and currents would then also be sources of electromagnetic energy, if one chooses vanishing initial conditions for the electromagnetic potentials? Because if the potentials are vanishing in the beginning, they would have to build up which basically means that electric fields would build up as well. However since the electric field has energy content then that would mean that the charges are "sources" of energy?