Page "Voltage source" Paragraph 2

An ideal voltage source is a mathematical abstraction that simplifies the analysis of electric circuits.

If the voltage across an ideal voltage source can be specified independently of any other variable in a circuit, it is called an independent voltage source.

Conversely, if the voltage across an ideal voltage source is determined by some other voltage or current in a circuit, it is called a dependent or controlled voltage source.

A mathematical model of an amplifier will include dependent voltage sources whose magnitude is governed by some fixed relation to an input signal, for example.

In the analysis of faults on electrical power systems, the whole network of interconnected sources and transmission lines can be usefully replaced by an ideal ( AC ) voltage source and a single equivalent impedance.