What quantity measures how well a material insulates, and where do copper, an axon's cytoplasm and Teflon fall on it? · Lobeworks/17

Resistivity, ρ\rhoρ, in ohm metres: a block of length LLL and cross-section AAA has resistance R=ρL/AR = \rho L/AR=ρL/A.

What quantity measures how well a material insulates, and where do copper, an axon's cytoplasm and Teflon fall on it?

Resistivity, ρ\rhoρ, in ohm metres: a block of length LLL and cross-section AAA has resistance R=ρL/AR = \rho L/AR=ρL/A. Copper is about 1.7×10−81.7\times10^{-8}1.7×10−8 Ω·m, an axon's cytoplasm about 1 Ω·m and PTFE (Teflon) above 101810^{18}1018 Ω·m, so a good insulator resists some 102610^{26}1026 times more than a good conductor. The cytoplasm's resistance per unit length is the rir_iri​ of the cable equations, the term a wider axon lowers.