E-Field and Voltage Units

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.

Examples     Electric fields
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