Find the potential `varphi` of an uncharged conducting sphere outside fo wihich a point charge `q` is located at a distance `l` from the sphere's centre.

Explanation

Potential `varphi` is the same for all the points of the sphere. Thus we calculate its value at the centre `O` of the sphere. Thus we can calculate its value at the centre `O` of the sphere, because only for this point, it can be calculated in the most simple way.
`varphi = (1)/(4pi epsilon_(0)) (q)/(l) + varphi` ...(1)
where the first term is the potentail of the charge `q`, while the second is the potential due to the charges induced on the surface of the sphere. But since all induced charges are at the same distance equal to the radius of the circle from the point `C` and the total induced charges is equal to zero, `varphi = 0`, as well. Thus equaction (1) is reduced to the from,
`varphi = (1)/(4pi epsilon_(0)) (q)/(l)`