Define resistivity. Write an expression for the resistivity of a substance. Give the meaning of each symbol which occurs in it.
By definitions the resistivity of a material of a conductor is the resistance offered by a unit length and unit cross-section of the conductor. It is intrinsic property of material.
The expression for the resistivity is
Where m = mass of the electron
N= number density of electron
E = charge on the electron
Ƭ = relaxation time.