An infinitely long wire is formed as in the diagram on your assignment. It is formed so that it has a circular portion of R = 50.0 cm and the straight portion is located at a distance r from the center of the circular portion. Find r (in cm) such that the net magnetic field at the center of the circular portion is zero. Ok so I am confused on this problem because there is no current mentioned, and all the equations giving involve current. Then I thought that the circle could be split in two and the force of the two halves would then have to equal zero but that seems wrong as well. Please help I just don't understand :(.