An extended notion of enthalpy. Electromagnetic solids

Some procedures are here expounded in order to introduce the physical and the material or configurational stress in deformable and moving solids. In electromagnetic materials, the electromagnetic fields are preliminarily introduced in the Lagrangian form. Then a variational approach is proposed through two different procedures. Two energy–momentum tensors are excerpted from the suggested procedures. One of them corresponds to a Cauchy-like stress and the other one to the material stress. The latter rules the balance law for the material momentum. This balance law across a first-order discontinuity surface addresses an extended notion of enthalpy and also an extension of the Maxwell condition in thermodynamical phase transitions of electromagnetic solids.