In physics, Ampère's law is the magnetic equivalent of Gauss's law. It was discovered by André-Marie Ampère It describes the relation between a circulating magnetic field in a closed loop and the generated electric current:
where
B is the magnetic flux
s is an infinitesimal element of the closed loop S
I is the current encircled by the curve S
μ0 is the permeability of free space
is the path integral along the loop S

This law, as the others laws of electromagnetism was later incorperated into Maxwell's equations, unifying all of electromagnetism.