Multiple Point Charges Alright so the question is: A charge of 1.2x10^-3C is fixed at each corner of a rectangle that is 30cm wide and 40cm long. What is the magnitude and direction of the electric force on each charge? What is the electric field and the electric potential at the centre? I am NOT asking for the answer, i am asking for someone to help push me along the right path. I have researched this on the internet and read about it in my textbook. This is what i have come up with. At each point, r1 = 0.3, r2 = 0.4, r3=0.5. E = vector sum And then use the equasion E=KQ/R not quite sure what to do at this point.