1. The problem statement, all variables and given/known data Use Ampere’s law to calculate the magnetic field inside of a toroid with 850 turns. The inner radius of the rectangular coils is 3.00 cm, the outer radius is 7.00 cm. 2. Relevant equations ampere's law: path integral(B*ds) over a closed path is equal to the enclosed current times mu_0 3. The attempt at a solution by ampere's law for toroids, I get B= mu_0*N*I/(2*pi*R) Im confused as to what the inner and outer radius have to do with this problem, hence the cry for help :( anyone ?