Statcoulomb

In physics, a statcoulomb (statC), formerly known as esu, is the unit of electric charge in the cgs-esu (centimeter-gram-second electrostatic system) of units. A point charge has magnitude one statcoulomb, if it repels a point charge of equal magnitude at a distance of 1 centimeter with a force of one dyne.

1 statC = 10/c C,

where C (coulomb) is the SI unit of charge and c is the cgs speed of light (c ≈ 3⋅10¹⁰ cm/s).