A charged particle P is situated in a vacuum at a distance 
from the centre of a charged conducting sphere of radius 
, as illustrated in the figure below.
For the particle P outside the conducting sphere, the charge on the sphere may be assumed to be a point charge at its centre. The sphere and the particle P are both charged positively.
State the direction of the force acting on particle P.
State the position of particle P for the force to be maximum.
