Question -
Answer -
The given figure shows a squareof side 10 cm with four charges placed at its corners. O is the centre of thesquare.
Where,
(Sides) AB = BC = CD = AD = 10 cm
(Diagonals) AC = BD = 
cm
AO = OC = DO = OB = 
cm
A charge of amount 1μC is placedat point O.
Force of repulsion betweencharges placed at corner A and centre O is equal in magnitude but opposite indirection relative to the force of repulsion between the charges placed atcorner C and centre O. Hence, they will cancel each other. Similarly, force ofattraction between charges placed at corner B and centre O is equal inmagnitude but opposite in direction relative to the force of attraction betweenthe charges placed at corner D and centre O. Hence, they will also cancel eachother. Therefore, net force caused by the four charges placed at the corner ofthe square on 1 μC charge at centre O is zero.