Question

Three point-like charges are placed at the corners of a rectangle as shown in the figure, a = 28.0 cm and b = 56.0 cm. Find the magnitude of the electric field at the center of the rectangle. Let q1 = q3 = +15.0 µC and q2 = −40.0 µC.

Answer 1

Center of rectangle is same distance away from both q₁ and q₃ .Also q₁ and q₃ are same and positively charge.So electric field at center due to both q₁ and q₃ charge are same and at opposite direction, which cancel out.

so electric field at center is only due to q₂ charge.