Electromagnetic

 Theory - 

*One of the basic theorems in electromagnetism is the Ampere’s Law which relates, the
magnetic field produced by an electric current, to the current passing through a conductor.

Ampere’s Law
Ampere’s Law states that the line integral of the
magnetic field H taken around a closed path is equal
to the total current enclosed by the path.

i.e. ∫ H ⋅ dl = ΣI

For a uniform field, H is a constant and we have

H . l = Σ I

or if H is constant over sections, with different sections having different H,
then
             Σ H . l = Σ I