1. The problem statement, all variables and given/known data This is from a lab program for my class. Its set on a grid where I can place charges and use the mouse pointer to find the intensity of the field at any spot. I am using the E values I got from hovering my mouse over the indicated spot (x, y). I have a positive 10 microcoulomb charge at (-140, 140). I have determined at (-100, 100), E=28.12 microcoulomb. They are asking me to find the constant of proportionality "k" at that point. I also have E=7.03 at (-60, 60), E=2.30 at (0, 0), and E=0.57 at (140, -140). 2. Relevant equations E=[k*q*r(hat)]/r^2 3. The attempt at a solution 28.12 = [k*10*56.6]/56.6^2 k = 159.2 I'm not sure about my r(hat) variable. I understand it to be the vector pointing from the charge to the other point. I used the distance formula to get r=56.6. q=10 microcoulomb is given in the problem. When I performed this equation for the next data set (-60, 60), I got k=79.5. I thought k would be a constant that was the same for all equations, as in the force equation F=[k*q(1)*q(0)*r(hat)]/r^2 where k = 8.99x10^9. Is k going to be constant, or will it change with different data? and How do I go about finding r(hat)? and What would be my units for k? (Nm^2/C^2)?