Figure 20-3, referred to below, is 0.800m wide and 0.400m tall with "A" in the top left corner, "+4 microC" charge in the top right corner, "+2 microC" charge in the bottom left corner, and "B" in the bottom right corner.
Two point charges of magnitude +4.00 μC and +2.00 μC are placed at the opposite corners of a rectangle as shown in Figure 20-3.
(a) What is the potential at point A due to these charges?
(b) What is the potential at point B due to these charges?
(c) What is the potential difference between points A and B?
U=(kQq)/r where k=8.99E9 Nm^2/C^2
The Attempt at a Solution
I honestly do not know where to begin this problem, other wise I wouldn't have posted it. I started by trying to plug values into "U=(kQq)/r" but quickly realized that would only help me if I knew the charge on points A and B.
This is what I had done before I realized I had no idea what I was doing:
U=(8.99E9*4*2)/0.89 (0.89 is the hypotenuse of the rectangle)
I was then going to plug that number into U=qV and solve for V, but I have no q for points A or B so I'm stuck.