Two charges q = 9.0μ C are fixed in space a distance d = 1.5 cm apart, as shown in the figure.
a) With V = 0 at infinity, what is the electric potential at point C?
b) You bring a third charge q = 9.0μC from infinity to C. How much work must you do?
c) What is the potential energy U of the three-charge configuration when the third charge is in place?
The Attempt at a Solution
I thought that I should find the distance between q and C using the pythagorean theorem.
((9E9)(9.0E-6)/(2.1213 cm))+((9E9)(9.0E-6)/(2.1213 cm))=7.64E4 V
But this didn't work. The online homework said it was wrong.
Is that the right equation to use? How does the V=0 at infinity affect this problem?