Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square?

Question

Quizplus · Accepted Answer

The net force acting on the charge at the center of the square is the vector sum of the forces due to the three charges at the corners. By symmetry, the force due to the top and bottom charges cancel out along the vertical direction, while the force due to the left and right charges add up along the horizontal direction. Therefore, the net force has a horizontal component pointing to the right, which is represented by arrow B.

Three Equal Charges +Q Are at Three of the Corners