The line integral of the magnetic induction field around any closed path is equal to

From Ampere’s Circuital Law 

Line integral to the magnetic field of the coil = μ_o times the current passing through it. It is mathematically expressed as

$\text{∮}\overrightarrow{\mathrm{B}}\cdot \overrightarrow{\mathrm{dl}}={\mathrm{\mu }}_0{\mathrm{I}}_{\text{enclosed }}$

Here μ₀ = permeability of free space = 4 π × 10^-15 N/ A² and

 ∫ B.dl = line integral of B around a closed path.