Two charges – q and + q are located at a and b respectively, constitute an electric dipole. Distance AB = 2a, O is the mid point of the dipole and OP is perpendicular to AB. A charges Q is placed at P, where OP = Y and Y >> 2a. The charge q experiences as electrostatic force F. If Q is now move along the equatorial line to P such that Op = (y/3), the force on Q will be closed to (y/3>>2a).