An electrical circuit is a network of components and connections used to transport electric charge and exchange energy. Resistors dissipate energy, capacitors store energy in an electric field, and inductors store energy in a magnetic field.
A lumped-element model represents the circuit by branch electric currents and terminal electric potential differences. Kirchhoff's current law expresses charge balance at connections, while Kirchhoff's voltage law relates the branch voltages around loops. [ref]
University Physics Volume 2 by Samuel J. Ling and others. Section 10.3, junction and loop rules, equations 10.4–10.5
For constant ideal components, with current entering the positive-voltage terminal,Combining these relations produces algebraic equations or time-dependent differential equations.For example, an RC circuit charging an initially uncharged capacitor from a fixed voltage source obeysThe product is its time constant. This transient connects energy storage to the rate of the circuit's response. [ref]
University Physics Volume 2 by Samuel J. Ling and others. Section 10.5, charging a capacitor, equations 10.8–10.10
When propagation along connections matters, a transmission line description can replace a single lumped model. New to topics? Read the docs here!