The given figure shows a square of side 10 cm with four charges
placed at its corners. O is the centre of the square.Where,
(Sides) AB BC = CD = AD = 10 cm
(Diagonals) AC = BD = 10$\sqrt{2}$ cm
AO = OC = DO = OB = 5$\sqrt{2}$ cm
A chase of amount l${}_{\mathrm{\mu }}$C is placed at point OForce of repulsion between charges placed at corner A and center O 1s equal in magnitude but opposite in direction relative to the force of repulsion between the charges placed at corner C and center. Hence, they will cancel each other. Similarly, the force of attraction between charges placed at corner B and center O is equal in magnitude but opposite in direction relative to the force of attraction between the charges placed at corner D and center O. Hence, they will also cancel each other. Therefore, the net force caused by the four charges placed at the corner of the square on l${}_{\mathrm{\mu }}$C charge at center O is zero.