A piece of copper wire has a resistance per unit length of 6.40e-3 ohm/m. The wire is wound into a thin, flat coil of many turns that has a radius of 0.190 m. The ends of the wire are connected to a 12.0 V battery. Find the magnetic field strength at the center of the coil. R/L = 6.40e-3 ohm/m r = 0.190 m V = 12.0 V u0 = 4pi e -7 Tm/A B = ? T Equations: V = IR (I = V/R) B = u0 * n * I so B = u0 * n * (V/R) I don't know where to go from here.