Derive an expression for the resistivity of a good conductor, in terms of the relaxation time of electrons.

Resistivity of a material of conductor in terms of relaxation time is given by

(i) Define the term drift velocity . (ii) On the basis of electron drift , derive an expression for resistivity of a conductor in terms of number density of free electrons and relaxation time. On what factors does resistivity of a coductor depend ? (iii) Why alloys like constantan and manganin are used for making standard restores ?

The relaxation time in conductors

Derive the expression for the current density of a conductor in terms of the conductivity and applied electic field. Explain with reason how the mobility of electrons in a conductor changes when the potential difference applied is doubled, keeping the temperature of the conductor constant.

Derive the expression for drift velocity of free electron in terms of relaxation time and electric field applied across a conductor.