In search of a convention for the use and teaching of multi-domain circuits

Circuit models have been used for many years to represent systems composed of concentrated elements that represent isolated and idealised physical phenomena. Disciplines such as electrical, mechanical and hydraulic engineering have used them to model and study related physical systems. The potential of circuit modelling has even led to its use in fields beyond engineering, such as chemistry and biology. Furthermore, this modelling allows for the inclusion of systems that are not purely energy-based, enabling the unification of complex systems spanning multiple domains into a single physical model. Despite the widespread use of these models, there is no agreement on the variables, parameters, and symbols used to describe these circuits, with different notations being used by different authors. This paper therefore proposes a convention for elements and properties for the description of multi-domain circuits that will enable the creation of a common language for representing physical systems in the fields of science and engineering. This is in order to take advantage of the graphical representation and analysis function of the schematic circuit and lay the foundations for its use in engineering education. The proposed convention will be complemented with examples of systems involving two or more energy domains, demonstrating the scope of its applications.