Resistivity OR specific resistance

“Resistivity OR specific resistance”: Resistivity is the obstruction provided by the unit volume of conductor. It is denoted by  (Rho).

We know that “At a given temperature the resistance of a conductor is directly proportional to the length l and inversely proportional to the area of cross section A.”

i.e     R ∝ l
And  R ∝ 1/A

Combining above both relation

        R ∝ l/A

        R = ρ×(l/A)

Here   (Rho) is proportionality constant which is known as resistivity of material of a conductor.

Again   R = ρ.l/A
    
    [ ρ = R×(A/l) ]

SI unit of ρ = ohm-metre

Dimension formula = [ML^3T^-3A^-2]