Chapter 12 - Circuit Elements and Circuit Variables

Abstract

The most complicated electrical and mechanical systems are constructed from a small set of basic elements. These elements fall into two general categories: active elements that usually supply energy to the system and passive elements that either dissipate or store energy. In electrical systems, the passive elements are described and defined by the relationship they enforce between voltage and current. In mechanical systems, the defining relationships are between force and velocity. These relationships are linear and involve only scaling, differentiation, or integration. Active electrical elements that supply well-defined voltage are termed voltage sources and those that supply a well-defined current are known as current sources. Active mechanical elements are categorized as either sources of force or sources of velocity (or displacement), although mechanical sources are generally far from ideal. All of these elements are defined as idealizations.