# Biot-Savart Law

A current element of length $\mathrm{d}\vec{l}$ carrying current $I$ produces a magnetic field at point P, \begin{align} \mathrm{d}\vec{B}=\frac{\mu_0}{4\pi}\frac{I\;\mathrm{d}\vec{l}\times\hat{r}}{r^2}, \end{align} where $\vec{r}$ is the position vector of P from the current element.