What was the Resistance?

Abstract

All materials have the ability to support some movement of charged particles, that is, to support “current”. The measure of this ability is termed conductivity and is typically designated by the Greek letter σσ (“sigma”). The higher the conductivity, the more readily that material supports current. The resistivity of a material is designated ρρ (“rho”) and is inversely related to the conductivity ρρ = 1/σσ. Some materials are very good at conducting current. Most of these are metals elements like copper, silver, and gold. Some materials conduct current very poorly like glass or many types of plastic.