# Physics:Electrostatic units

The electrostatic system of units (CGS-ESU) is a system of units used to measure quantities of electric charge, electric current, and voltage within the centimetre–gram–second (or "CGS") system of metric units. In electrostatic units, electrical charge is defined by the force that it exerts on other charges.[1][2] Although CGS units have mostly been replaced by the International System of Units, electrostatic units are still in occasional use in some applications, most notably in certain types of physics such as in particle physics and astrophysics.

The main electrostatic units are:

The CGS-ESU units for magnetic quantities are seldom used,[3] and don't have special names. Sources tend to just use 'esu' or the derived unit expressed in terms of the CGS base units. For example, the unit for magnetic induction is g1/2/cm3/2, corresponding to ccgs gauss, and corresponding to ccgs×10−4 tesla, where ccgs = c/(cm/s) = 29979245800 is the numeric part of speed of light c expressed in CGS units.[4][5]