Voltage

Voltage, electromotive force, or potential difference is the difference in electrical potential between the positive and negative poles of a battery or other device that generates a flow of electrons. The units of electrical potential in the SI and most other systems of units are volts.

Electrical potential difference can be analogized by comparing to gravitational potential difference, the difference in potential energy per unit of mass between two objects at different elevations in a gravitational field. It can also, perhaps more usefully, be compared to pressure differences in hydraulic systems, with current flow analogized as the quantity of water flow, resistance as the size and roughness of the pipe or channel.