Common Cases of Ampère's Law

Distance $r$ away from an infinitely long wire $B=\frac{{\mu }_{0}I}{2\pi r}$ Inside a Solenoid with $n$ turns per unit length $B={\mu }_{0}nI$Inside a toroidal Solenoid with total $N$ turns $B=\frac{{\mu }_{0}NI}{2\pi r}$