define resistivity.write an expression for the resistivity of a substance.give the meaning of each symbol,which occurs in it.
(b)state the si unit of resistivity.
(c)distinguish between resistance and resistivity.
Resistivity is the measure of a material’s ability to oppose the flow of current . Resistivity of a conductor is a property of the material of the conductor.
Unit of resistivity is Ohm meter, Ω m .
Resistivity of the material of the conductor changes with temperature.
Following is the equation relating resistivity (ρ) and resistance (R) of a conductor of length (L) and area (A).
ρ = AR / L