Ampère's Law relates the magnetic field around a closed loop to the electric current passing through that loop. It states that the line integral of the magnetic field B around a closed path is proportional to the total current I enclosed by that path. This relationship is fundamental in understanding how electric currents generate magnetic fields. The law is mathematically expressed as ∮B·dl = μ₀I, where μ₀ is the permeability of free space. Ampère's Law is a key principle in electromagnetism and is used in various applications, including the design of electrical devices like transformers and inductors.