# specific resistance or Resistivity definition , formula , example , difference , unit

definition , formula , example , difference , unit of specific resistance or Resistivity : when a current flows through a conductor then the resistance of the conductor resists or opposes the flow of current.
So resistance is defined as
resistance is a property of a conductor which opposes the flow of electric current through the conductor.
The resistance of any wire is depend on the length of the wire , cross sectional area of the wire , type of the material by which the wire is made and the operating temperature.
Let us suppose the length of wire is L and cross section area of this wire is a .
And we know that the resistance of wire is directly proportional to the length of the wire and also the resistance of wire is inversely proportional to the cross sectional are
It means
R ∝ L/a
R = ρL/a
Here ρ (rho) is a constant which is called the specific resistance or resistivity of the material by which the wire is made up.
The rho (ρ) means resistivity (specific resistance ) depends on the nature of the material of wire.
To defined the ρ (rho) we assume the length of the wire is 1 and the cross sectional are is also 1 .
then the ρ will be
putting L = a =1 in formula
R = ρ
the ρ is defined as
resistance of a material of unit length and unit cross section area is called resistivity or specific resistance.
The MKS or SI unit of rho (ρ) or resistivity is ohm-meter (Ω-m) or ohm per meter.