Define relaxation time of the free electrons drifiting in a conductor. Establish a relation between

Mobility of free electrons in a conductor is

Define atomic mass unit and electron volt. Establish a relation between them.

The relaxation time in conductors

Define surface density of charge and potential of a charged and potential of a charged spherical conductor. Establish a relation between them.

If n ,e,m and tau are free electron density in conductor , charge of electron, mass of electron and relaxation time of free electrons , then resistivity rho of the conductor can be expressed as