A this disc of dielectric material, with a total charge +q distributed uniformly over its surface, rotates with angular speed `omega` about an axis perpendicular to the disc and passing through its centre .Find the magnetic moment with its angular momentum , assuming that its mass is m.
[Hint : Consider a ring of radius x and thickness dx. Calculate charge on it and then the current consituited by its rotation .Find its magnetic moment and integrate for the whole disc.]

Answer

`(1)/(4)qwr^(2),(q)/(2m)`