State and explain Biot savart law.

The magnetic induction field strength at a point due to a current carrying element is

directly proportional to current 'i' $\mathrm{dB\alpha i}\to \left(1\right)$
directly proportional to length of the element ${\text{ 'dl}}^{\mathrm{\prime }}\text{. i.e }\mathrm{dB\alpha d}l\to \left(2\right)$
directly proportional to sine of angle between the current carrying element and the line joining the mid point of element
$\mathrm{dB\alpha sin}\mathrm{\theta }\to \left(3\right)$
and is inversely proportional to the square of the distance between the point and element
$\begin{array}{l}\mathrm{dB\alpha }\frac{1}{{\mathrm{r}}^2}\to \left(4\right)\\ \mathrm{dB\alpha }\frac{\mathrm{id}l\sin \mathrm{\theta }}{{\mathrm{r}}^2}\\ \mathrm{dB}=\frac{{\mathrm{\mu }}_0}{4\overline{\mathrm{\pi }}}\frac{\mathrm{id}l\sin \mathrm{\theta }}{{\mathrm{r}}^2}\end{array}$