Question

White Ampere's circuital law ? Obtain an expression for the magnitic field due to a
long straight current carrying conductor using Ampere's circuital law.

Answer 1

Ampere's circuital law states that line integral of magnetic field forming a closed loop around the current carrying wire, in the plane normal to the current, is equal to the μo times the net current passing through the close loop.

∮→B⋅→dl=μ0I, where μ0 is the permeability of free space.

This is the required expression.