Kirchhoff´s laws and Tellegen´s theorem for networks and continuous media

This paper addresses the relation between network theory and quasistatic field theory. The fundamental orthogonality relations (Tellegen\´s theorem for circuits-a generalization of it given here for fields) are derived by parallel routes for the two disciplines. To illustrate that this parallel development can produce new insights, a standard integral theorem from vector calculus suggests a novel formulation of Tellegen\´s theorem for -terminal elements.