potential difference

Difference in the electrical potential (see potential, electric) of two points, being equal to the electrical energy gained by a unit positive electric charge moving from one point to the other. Electrons (which are negatively charged) flow in a conducting material towards the part that is relatively more positive (fewer negative charges). The SI unit of potential difference is the volt (V). The potential difference between two points in a circuit is commonly referred to as voltage (and can be measured with a voltmeter). See also Ohm's law.

One joule of energy is gained by each coulomb of charge when moved through a potential difference of one volt. Potential difference V may be represented by the equation V = E/Q, where E is the electrical energy converted in joules and Q is the charge in coulombs. Chemical energy from a battery is converted to electrical energy in a circuit, this energy being given by rearranging the above formula: E = Q × V.