Zur Thermodynamik des elektromagnetischen Feldes in der kontinuierlichen Materie

Abstract

The following questions are discussed. Does the electromagnetic field energy add to the internal energy or to the free energy? What are density of momentum and flow of energy in the presence of an electromagnetic field? How is the electromagnetic force density to be formulated in the best way? With respect to the first question, various thermostatic potentials are considered. The other questions find an answer from a relativistic formulation of the equations of motion. In particular it is shown that the various definitions of the pressure which arise from the manifold of thermostatic potentials and which lead to different expressions for the electromagnetic force density are irrelevant if, instead, one uses the gradients of the unambiguous chemical potential and of the temperature, multiplied by the entropy density, as parts of the total force density.