There is a charge Q in the cavity of a metal ball of radius R. Find the charge induced by this charge on the surface of the cavity. Why will the charge be distributed with a constant density on the surface of the ball? What is the surface charge density of a sphere if its total charge is zero? Find the electric field strength outside the ball at a distance L from its center if its total charge is q. Does this field depend on the location of the cavity in the ball? from its shape?