Potentialforskellen

Potentialforskellen, or potential difference, is the difference in electric potential energy per unit charge between two points in an electric field. It is a scalar quantity and is measured in volts, usually denoted ΔV, with ΔV = V(b) − V(a) for two points a and b.

The potential difference represents the work per unit charge required to move a positive test charge from point a to point b against the electric field. In mathematical terms, ΔV = W_ext/q, where W_ext is the work done by an external agent if the move is performed quasistatically. In electrostatics, ΔV is also related to the electric field E by ΔV = −∫ from a to b of E · dl, and the field and potential are connected by E = −∇V. This implies that moving from higher to lower potential can release energy as the field does work on the charge.

The SI unit of potential difference is the volt (V), with 1 V = 1 joule per coulomb (1 J/C). In electrical circuits, potential differences drive current and are created by sources such as batteries and power supplies across components. While in static (electrostatic) fields the potential difference between two points is independent of the path taken, in time-varying magnetic fields the same integral can depend on the path.

Commonly, the potential difference between the terminals of a battery is cited as its voltage, for example a 9-volt battery.