A circular wire loop with a diameter of 0.2m and a long, straight wire carry currents, I(1) AMP and I(2) AMP, respectively. Both wires are located in the plane of the page, and the distance between the long wire and the center of the circle is 0.15m. What is the magnitude of I(1) if the magnetic field at point O is zero when I(2) = 3 AMP? Here's where I get stuck. I know that I'm supposed to use the equations: B= μ0*I/2*pi*d and B= μ0*N*I/2*r I re-arranged the equations to figure out that to solve for I(1) it would be I(1)= B*2*r/μ0N N = 1, since it's a single loop r = .1m μ0 = 4*pi*10^-7 I think I'm supposed to solve B from the straight wire equation, so I re-arranged that equation to: I(2) = B*2*pi*d/μ0 I(2) = 3 AMP d = .15m etc... But the question asks: what is the magnitude of I(1) if the magnetic field (B) at O is zero when I(2) = 3 AMP Does that mean the answer would also be zero? How then would I determine direction of I(1)? Clock-wise or Anti-clockwise? Please help. I've confused myself. Thanks.