19th Century Pioneer

Heinrich Friedrich Emil Lenz (1804 – 1865).  Russia

He was a Russian scientist that made a significant contribution to the understanding and use of electromagnetism with the discovery that an induced electric current flows in a direction so that the current opposes the change that induced it. 

Example:  Pushing a bar magnet through a coil of wire will induce electric current into the coil, in turn, the current sets up a magnetic field around the coil.  Lenz’z law indicates the direction of the induced current.