3) A square with sides of length L has a point charge at each of its four corners. The upper left and lower right corners have charges with q = +3.30 C the other two diagonal corners have charges Q. Find the magnitude and sign of the charges Q such that each of the 3.30 C charges experiences zero net force. Hint: Did you draw a picture? I suggest you pick 3 of the charges as sources and find the net E-field that they produce at the location of the 4th charge. You want the net force acting on the 4th charge (one of the Q's) to be zero. - answer: Q = 1.17 C