This law describes the quantities that influence the electrical resistance of a conductor, as cited in its statement:
The resistance of a homogeneous conductor of constant cross section is proportional to its length and the nature of the material of its construction, and is inversely proportional to the area of its cross section. In some materials it also depends on your temperature.
Being expressed by:
ρ = resistivity, depends on the conductor material and its temperature.
ℓ = conductor width
A = cross-sectional area.
Since the electrical resistance unit is ohm (Ω), then the unit adopted by SI for resistivity is .