Materials can be divided into three categories according to their ability to conduct an electric current:
Conductors have electrical resistivity on the order of 10-8 to 10-4 Ωcm whereas insulators have electrical resistivity on the order of 108 to 1018 Ωcm. Semiconductors have an electrical resistivity value between those of conductors and insulators—10-4 to 108 Ωcm.
Electrical resistivity: Ωcm
Electrical resistance (R) is the resistance to a flow of electric current through a material. The electrical resistance of a material is proportional to its length (l) and inversely proportional to its cross-sectional area (A). Each material has also an intrinsic property called electrical resistivity (ρ). Electrical resistance (R) is expressed as follows as a function of ρ, I and A. Electrical resistivity (ρ) is determined by the energy level (band) of the electrons in the outermost shell of an atom, crystalline states, and other factors.