1. Reminders

1.1 Electrical conductivity of materials

Electrical conductivity σ is the inverse of resistivity; it is expressed in siemens per meter (S/m) while resistivity ρ is expressed in ohms meters (Ω · m).

Materials can be classified as conductors, semiconductors and insulators, according to their electrical behavior at ambient temperature.

The only indisputable insulator is an absolute vacuum. For all other materials, whether solid, liquid or gaseous, electrical conductivity exists under certain conditions that differ from one material to another and according to the type of conductivity specific to that material. For example, glass, which is insulating at room temperature, becomes highly conductive at temperatures above 500 ˚C. It is common...