In physics, the relative electrical state of an object. A charged conductor, for example, has a higher potential than the Earth, whose potential is taken by convention to be zero. An electric cell (battery) has a potential in relation to emf (electromotive force), which can make current flow in an external circuit. The difference in potential between two points—the potential difference—is expressed in volts; that is, a 12 V battery has a potential difference of 12 volts between its negative and positive terminals.