毕奥-萨伐尔定律

Biot-Savart Law

Thsi equation describes the magnetic field generated by electric current.

$$dB = \frac{\mu_o}{4\pi} \cdot \frac{I \vec{dl} \times{\hat{r}}}{r^2}$$ $$dB = \frac{\mu_o}{4\pi} \cdot \frac{I \vec{dl}\sin \theta}{r^2}$$

$\mu_o = 4 \pi \times 10^{-7}$

$\hat{r}$ is a unit vector that specifies the direction of the vector distance $r$ from where the current is to the point on the field.

Everything in the equation is a constant except $dl$ which is constantly changing