Resistance and Resistivity

Resistivity depends on the nature of the material rather than its dimensions, whereas the resistance of a conductor depends on its dimensions as well as on the nature of its material.

R ∝ l

R ∝ 1/A

R ∝ l/A

R = ρ l/A

where ρ is a constant for the material at constant temperature. It is called the specific resistance or resistivity of the material.

Resistivity of a material is the resistance offered by a wire of length one metre and area of cross section one m². The unit of resistivity is ohm metre (Ωm).

Reciprocal of resistivity is called conductivity (specific conductance) and is denoted by σ.

σ = 1/ρ