Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force.

## Uses of the term

The term is most frequently used as an abbreviation of 'electrical potential difference' (see below), which is almost synonymous with 'voltage', but it also occurs in many other branches of physics.

## Explanation

Potential difference is the difference in some quantity between two points in a conservative vector field  of that quantity. Some examples are listed below.

• In mechanics, the gravitational potential  difference between two points on Earth is related to the energy that would be required to move a unit mass from one point to the other against the Earth's gravitational field . Unit: joules per kilogram.
• In electrical engineering, the electrical potential difference ('voltage') between two points is related to the energy that would be required to move a unit of electrical charge from one point to the other against the electrostatic field that is present. Unit: joules per coulomb = volts.
• In fluid systems the potential difference is the difference in pressure. Unit: pascals.
• In thermal systems the potential difference is the difference in temperature. Unit: kelvins.

In engineering, potential is sometimes described as the across variable, whereas flux is the through variable. The product of the flux and the potential difference is the power, which is the time rate of change of energy.