Expressing the Units of Electricity and Magnetism Directly in the MKS System

Abstract

Since the unit of electric charge can be chosen independently of the value of the permittivity of free space ε₀, it is shown that all electromagnetic quantities can also be assigned units directly in the MKS system.  For example, the unit of electric charge can be 1 J as long as ε₀ has units of 1 N.  A table is given that makes a comprehensive comparison of the standard units in the Giorgi system with those in two such direct MKS schemes.  A simple procedure is also described for changing the numerical values of the units in a systematic manner by dividing the various electromagnetic quantities into five distinct classes.  This allows one to equate the value of ε₀ to 1/4Ï€, for example, similarly as for the Gaussian system of units, while still retaining the same formulas as in the Giorgi system.