physics
posted by Sarah .
Identical +7.74 μC charges are fixed to adjacent corners of a square. What charge (magnitude and algebraic sign) should be fixed to one of the empty corners, so that the total potential at the remaining empty corner is 0 V?
I thought that this is what i should do. But I cant get the correct answer...
the total potential is
V = k[7.74μC/r + 7.74μC/√2 *r + q/r]
0 = k/a[(7.74μC+q)√2 + 7.74μC]
or (7.74μC+q)√2 =  7.74μC
q = 7.74μC[1+1/√2]

correct.

So that gives me q=13.23. I am told that that is the wrong answer. Please help!