The relation of Tellegen's theorem to the continuous field equations revisited

Tellegen’s theorem for networks is directly derived from Maywell’s equations. As for general circuits including capacitors and inductances, non-vanishing displacement currents and temporally varying magnetic fluxes are present, in the presented approach domains containing lumped elements are treated such that the utilization of an electric potential and of Kirchhoff’s current law can be maintained in the considered field domain. The procedure works for the general form of Tellegen’s theorem including nonlinear elements and relating topologically equal but otherwise different networks.