Voltage:

The basic unit of measure for potential difference is the volt (symbol V), and, since the volt unit is used, potential difference is known as voltage.  An object's electrical charge is determined through the number of electrons in which the object has gained or lost.  Since such a huge number of electrons move, a unit known as the "coulomb" is used to denote the charge.  A single coulomb is equal to 6.28 x 10¹⁸   (billion, billion) electrons. For instance, it has gained 6,280,000,000,000,000,000 extra electrons if an object gains one coulomb of negative charge.  A volt is declared as a difference of potential causing one coulomb of current to do one joule of work.  A volt is also defined as in which amount of force needed to force one ampere of current by one ohm of resistance.  A latter is the definition along with that we will be most concerned in this module.