Question

describe ampere's circuital law.

Answer 1

the line integral of magnetic field B around any closed path in vacuum / air is equal to ц°times the total current enclosed by that path

Answer 2

Ampere's circuital law states that the closed line integral along the closed loop of  magnetic field is equal to Mu times the net current that (enclosed by) passes across the closed loop region.

$\int\limits^O_. {B} \, dl = Mu\ I$