Question

Four point charges are located at the corners of a square with sides of length a . Two of the charges are +q, and two are -q.

Find the magnitude of the net electric force exerted on a charge +Q, located at the center of the square, for the following arrangement of charge: the charges alternate in sign (+q,-q,+q,-q) as you go around the square.

Find the direction of the net electric force exerted on a charge +Q, located at the center of the square, for the following arrangement of charge: the charges alternate in sign (+q,-q,+q,-q) as you go around the square.

Find the magnitude of the net electric force exerted on a charge +Q, located at the center of the square, for the following arrangement of charge: the two positive charges are on the top corners, and the two negative charges are on the bottom corners.

Find the direction of the net electric force exerted on a charge +Q , located at the center of the square, for the following arrangement of charge: the two positive charges are on the top corners, and the two negative charges are on the bottom corners.

Answer 1

Part 1: Diagonal forces are equal and opposite so they cancel to 0

Part 2: No net direction of translational motion as the net force on +Q is 0

Part 3: F=(4sqrt(2)kqQ)/a^2; use coulomb's law

Part 4: Direction is downwards as the positive forces at the top are repulsive and push away and negative charges on bottom are attractive and pull +Q toward them.