Resistivity (Rho) is defined as the resistance of a conductor of 1 m length and 1 qmm cross-section (A) at a temperature of 20 degrees Celsius. It depends on the material and its unit is Ohm x qmm/m.
The reciprocal of resistivity is conductivity. The resistivity is a fixed material constant. It changes with temperature depending on the temperature coefficient. From the resistivity, the conductor cross-section and the conductor length, the ohmic resistance (R) of the conductor can be calculated. To do this, the resistivity (Rho) is multiplied by the quotient of the conductor length to the conductor cross-section (rho x l/A).
The resistivity (Rho) of conductors lies between 0.01 and 0.2, that of non-conductors between `10^3` and `10^12`.