A long round dielectric cyclinder is polarized so that teh vector `P = alpha r`, where `alpha` is a positive constant and `r` is the distance from the axis. Find the space density `rho'` of bound chagres as a function of distance `r` from the axis.

Explanation

Given `vec(P) = alpha vec(r )` = distance from the axis. The space density of charges is given by , `rho' = - di v vec(P) = -2 alpha`
On Using, `di v vec(r ) = (1)/( r) (del)/(del r) (vec(r ). vec(r )) = 2`