A dielectric ball is polarized uniformly and statically. Its polarization equals `P`. Taking into account that a ball ploarized is this way may be represented as a result of a small shift of all positive chagres 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 `varphi = p_(0) r//4pi epsilon_(0)`, where `p_(0)` is the electric moment of the ball, and `r` is the distance from its centre.