posted by Joe .
There are two particles of charge +Q located on the top left and bottom right corners of a square. What is the direction of the net electric field at the point on the bottom left corner of the square? And also what would be the general equation be for finding the potential energy of a particle of charge q at this point on the bottom left of the square?
For your first question, perform a vector addition of the two fields due to partiles at the adjacent corners. The two fields will be at right angles and with field strangth kQ/a^2
a is the side length of the square.
For your second question, perform a scalar addition of the potential due to each adjacent corner particle. That should give you 2 k Q/a