A dielectric ball is polarized uniformly and statically. Its polarization equals P. Taking into account that a ball polarized in this way may be represented as a result of a small shift of all positive charges of the dielectric relative to all negative charges,
(a) Find the electric field strength E inside the ball;
(b) Demonstrate that the field outside the ball is that of a dipole located at the centre of the ball, the potential of that field being equal to (p = p0r/dae0, where P0 is the electric moment of the ball, and r is the distance from its centre.