Ans. Ampere’s law: The line integral of magnetic field $B$ along a closed path is equal to $\varepsilon_{\circ}$ times the total current enclosed by the path.
$\oint B.dl =\mu_{\circ}i$
Biot-savarts law:The magnitude of the magnetic field $dB$.
i) Directly proportional to the current $dB\propto i $
ii) Directly proportional to the length of the element $dB\propto dl$
iii) Directly proportional to the sine of the angle between the current and the element. $dB\propto sin\theta $
iv) Inversely proportional to the square of the distancer. $dB\propto \frac{1}{r^{2}}$
$$\therefore \, dB=\frac{1}{4\pi \varepsilon_{\circ} }\, \frac{i \,dl \,sin\theta}{r^{2}}$$