Units for electric potential and fields

Electric forces are measured in Newtons (N), electric potential energies are in Joules (J), and electric charge is measured in Coulombs (C). Since electric fields and potentials are obtained by dividing the force and potential energy by the charge, they are measured in units of N/C and J/C respectively. But a "Joule per Coulomb" (J/C) is also known as a volt (V), and the electric potential is thus often referred to as the voltage. The electric field can therefore also be quoted in units of volts per meter, since V/m = N/C.

Pairs of Equivalent Units

 Electric field V/m N/C Electric potential V J/C Force CV/m N Potential Energy CV J

A convenient unit of potential energy for describing microscopic physics, such as the energy of an electron in an atom, is the electron volt (eV). One electron volt is the potential energy change caused by moving one electron's worth of charge, e, through an electrical potential difference of one volt. Hence one electron volt equals 1.602E-19 J. Related units are keV, MeV, GeV, and TeV, which represent 103, 106, 109, and 1012 eV. These units will be used in nuclear and particle physics later in the semester.