Deduce the expression for resistivity.

Define the term resistivity and write its S.I. unit. Derive the expression for the resistivity in terms of number density of free electrons and relaxation time.

Deduce the expression for the magnetic dipole moment of an electron orbitting around the central nucleus.

A solenoid of length 'l' having n turns carries current 'I'. Deduce the expression for the magnetic field in the interrior of the solenoid.

An electron revolves in a circular orbit of radius r with uniform angular speed omega . From the expression for magnetic field due to current carrying circular conductor, deduce the expression for magnetic field at the center of electron orbit.

A charge q of mass m moving with velocity v, at right angles to a uniform magnetic field B. Deduce the expression for the radius of the circular path it describes.

A proton and an alpha -particle enter a uniform magnetic field perpendicularly with the same speed. How many times if the time period of alpha -particle than that of proton? Deduce the expression for the ratio of the radii of the circular paths of two particles.

Deduce the expression for the potential energy of a system of two point charges q_1 and q_2 brought from infinity to the points vecr_1 and vecr_2 respectively in the presence of electric field vecE .

Define relaxation time of the electrons drifting in a conductor. How is it related to the drift velocity of free electrons? Use this relation to deduce the expression for electrical resistivity of the material.

Define magnetic field intensity at a point and derive an expression for it at a point on the axial line of magnetic dipole. Also deduce the expression for small dipole.