Figure shows a uniformly charged sphere of radius R and total charge Q. A point charge q is situated outside the sphere at a distance r from centre of sphere. Find out the following :
(i) Force acting on the point charge q due to the sphere.
(ii) Force acting on the sphere due to the point charge.

Explanation

(i) Electric field at the position of point charge `vec(E)=(KQ)/r^(2) hat(r)`
So, `vec(F)=(KqQ)/r^(2) hat(r)" "|vec(F)|=(K qQ)/r^(2)`
(ii) Since we know that every action has equal and opposite reaction so `vec(F)_("sphere")=(K qQ)/r^(2) hat(r)`
`vec(F)_("sphere")=(K qQ)/r^(2)`