It can be described as an unbroken path along which an electric current may flow.

A simple circuit consists of a voltage source, such as battery (Cell, in electricity) or a generator, whose terminals are connected to those of a circuit element, such as a resistor, through which current can flow.

More complex circuits include additional sources or elements and perhaps Switches, so interconnected that, when appropriate switches are closed, each element is included in a closed path that also contains a source.

Series, parallel, and non-series-parallel connections are illustrated in the figure. The effective Resistance of two-series connected resistors is the sum of the individual resistance.

The effective conductance of two parallel-connected resistors is the sum of the individual conductances.