A review of the variational methods for solving DC circuits

TL;DR

This paper reviews variational principles in physics and their application to solving DC circuits, highlighting their connection to thermodynamics and potential educational benefits.

Contribution

It provides a comprehensive review of variational methods for DC circuits and explores their fundamental links to entropy production principles.

Findings

Variational principles can effectively solve DC circuits.

These methods relate to entropy production in thermodynamics.

Educational advantages of introducing variational techniques are discussed.

Abstract

Direct current (DC) circuits are usually taught in upper-level physics curricula, and Kirchhoff's laws are stated and used to solve the steady-state currents. However, students are not often introduced to alternative techniques, such as variational principles, for solving circuits. Many authors have tried to derive the steady-state distribution of currents in circuits from variational principles, and the initial attempts were carried out by great physicists, such as Kirchhoff, Maxwell and Feynman. In this article, we shall review such variational principles in physics and illustrate how they can be used to solve DC circuits. We will also explore how they are related, in a fundamental way, to the entropy production principles of irreversible thermodynamics. We believe that the introduction of variational alternatives for solving circuits can be a good opportunity for the instructor to present the techniques of the calculus of variations and irreversible thermodynamics to students.