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## Homework Statement

Four charges are arranged on the corners of a square whose edge length is

*a*. Two positive charges +Q are placed on diagonally opposite corners, and two negative charges -Q are placed on the other corners. (a) What is the force on a test charge q

_{o}placed at the center of the square? (b) What are the magnitude and the direction of the force on the test charge q

_{o}if it is placed at the midpoint of one of the edges?

## Homework Equations

Coulomb's Law-

F=[tex]\frac{k |Q1| |Q2|}{r

^{2}}[/tex]

## The Attempt at a Solution

(a)

I drew myself a picture of all the forces in a square with 1 set of diagonals positive and the other set negative. "a" represents the side length.

I'm not really sure where to go with this. I tried Coulomb's law for repulsive forces on q

_{o}by Q1, etc. and then did the same for attractive forces. The test charge is positive correct?

(b) I think I have this part figured out. Because all sides have one positive charge and one negative charge it doesn't matter which midpoint q

_{o}is placed on. If q

_{o}is positive then it will be repelled by +Q and attracted by -Q in a linear way. The only thing I'm unsure of is the two remaining charges not on the same line. Do they have any effect on the force of q

_{o}?

Instead of just posting an answer is it possible for you to show your thoughts/steps? I'd like to know the thought process for this type of problem instead of just the answer. Thanks for your help.