centimeter-gram-second
electrostatic system of units

Symbol, esu. In this system an electric unit was provided by describing the size of a charge in terms of a force. If you have ever attracted or repelled with a comb rubbed against your clothing, you have observed a force acting between charged bodies.

Imagine two bodies with electric charges, Q₁ and Q₂ respectively. Coulomb's Inverse Square Law for electrostatic charges describes the force between them:

Force is proportional to the product of Q sub one and Q sub two, over epsilon times r squared.

where F is the force, r is the distance (which has to be considerably larger than the bodies themselves), and ε (epsilon) is what is called the permittivity of the medium between the charges.

In the cgs system force is in dynes. The dyne has the dimensions

Grams times centimeters over seconds squared. ,

so let r be in centimeters. To define the unit of charge in the cgs electrostatic system of units, ε is disposed of by defining its value as equal to 1 for a vacuum. Inserting the other dimensions into Coulomb's law, the dimensions of the unit of charge are seen to be:

$A fraction. The numerator is the square root of the product of grams, centimeters cubed, and the unit of epsilon. The denominator is seconds.$

This unit is called the esu unit of charge, the electrostatic unit of charge, or the statcoulomb. All the other esu units are defined in terms of the esu unit of charge and the centimeter, gram, and second. To distinguish cgs electrostatic units from units in the international system, they were sometimes given the prefix “stat-”.

unit	properties
statampere	current
statvolt	electric potential difference, electromotive force
stattesla	magnetic flux density
statohm	resistance
statweber	magnetic flux
statfarad	capacitance
stathenry	inductance
statmho	conductance, admittance, susceptance

centimeter-gram-secondelectrostatic system of units

centimeter-gram-second
electrostatic system of units