A material's resistivity or specific resistance is a measure of the resistance it provides to the flow of electricity through it. It is a material's inherent quality. Specific resistance is determined by the material's composition, pressure, and temperature. Specific conductance, or the capacity to conduct electricity, is defined as the reciprocal of resistivity. The resistivity of conductors is quite low, whereas that of insulators is very high. A material's resistivity is a scalar quantity. Specific resistance, like every other physical property, requires a number linked with a unit.
A conductor's resistance R is determined by its length L, crosssection A, and composition. The resistance of a conductor with a constant crosssection is proportional to its length. For a certain length, the resistance is inversely proportional to the crosssection. These two dependencies may be written as a pair as,
R ∝ L/A
R = L/A
The particular resistance is a proportionality constant in this case. For various materials, the constant has varying values. Specific resistance is determined by the material's physical qualities, such as density and composition. For unit length and unit crosssectional area, L=1 and A=1, respectively.
= R
Resistivity may be defined using this condition.
The resistivity or specific resistance of a material is defined as the resistance of a homogenous chunk of that material of unit length and unit crosssection. Quantitatively,
Material conductivity is defined as the inverse of resistance.
According to the particular resistance formula,
When resistance R is stated in Ohms () and distances are expressed in centimetres, one usable unit is produced (cm). The unit of resistivity in this system is Ohmcm (.cm).
When lengths are measured in metres (m), the SI unit of specific resistance is Ohmm (.m). Ohm1 m1 or siemens m1 is the SI unit of conductivity (S . m1).
Metals conduct electricity well, but insulators can transport little to no current.
Metals have a relatively low specific resistance (108.m), whereas common insulators have quite high values (1016.m). The resistivity values at 20 degrees Celsius for various common materials are shown below.




























Copper has a specific resistance of 1.68 x 108. m (20 degree celsius), which means that the resistance between two opposed sides of a copper cube of 1 m is 1.68 x 108 at temperature 20 degree celsius. Copper has a conductivity of 5.96 x 107 Sm1. Copper's resistance to current flow is minimal due to its extremely low resistivity and high conductivity. Copper wires are commonly used to carry electricity in electrical circuits.