It was formulated in 1820, when a Lyonnese professor observed Oersted's discovery that the needle on a compass would line up perpendicular to a current-carrying wire.  
It was formulated in 1820, when a Lyonnese professor observed Oersted's discovery that the needle on a compass would line up perpendicular to a current-carrying wire.  Although it produces a very difficult equation, in cases of high symmetry it can be much easier to solve than the Biot-Savart Law.  FTP, name the law which states that the path integral of a magnetic field around any closed path is proportional to the current enclosed by the path, named for its French discoverer.
It was formulated in 1820, when a Lyonnese professor observed Oersted's discovery that the needle on a compass would line up perpendicular to a current-carrying wire.  
Ampere's Law