Four point charges q₁= 2 μC, q₂ = –5 μC, q₃ = 2 μC, and q₄ = –5 μC are located at the corners of a square ABCD of side 10 cm. What is the force on a charge of 1 μC placed at the centre of the square?

Imagine a figure showing a square of side 10 cm with four charges placed at its corners. O is the centre of the square.

Where, Four point charges q_A= 2 µC, q_B = -5 µC, q_C = 2 µC, and q_D = -5 µC are located at the corners of a square ABCD of side 10 cm.

(Sides) AB = BC = CD = AD = 10 cm

(Diagonals) AC = BD = 10√ 2 cm

AO = OC = DO = OB = 5√ 2 cm A charge of amount lµC is placed at point O.

Force of repulsion between charges placed at corner A and centre O is equal in magnitude but opposite in direction relative to the force of repulsion between the charges placed at corner C and centre O. Hence, they will cancel each other. Similarly, force of attraction between charges placed at corner B and centre O is equal in magnitude but opposite in direction relative to the force of attraction between the charges placed at corner D and centre O. Hence, they will also cancel each other. Therefore, net force caused by the four charges placed at the corner of the square on 1 µC charge at centre O is zero.