For a good conductor, E c o n d u c t o r is negligible, so we have, to a good approximation, L d I d t = ∫ ∫ 1 2 E c e n t e r l i n e ⋅ ⋅ d ℓ ℓ = V 1 − − V 2 , where V is the electric scalar potential along the centerline between points 1 and 2.