In April 1820, during a course in electricity which he was giving to his students, Orsted discovered the relation between electricity and magnetism in an experiment which today appears to us as very simple. He demonstrated that a wire carrying current was able to move the magnetic needle of a compass. There could therefore be an interaction between the electric forces on one hand and the magnetic forces on the other hand, which was revolutionary at the time.
However, on the 21st of July 1820, he published his experimental results in a 4 pages Latin article entitled : “Experimenta circa effectum conflictus electrici in acum magneticam”. His writings were translated and disseminated throughout the European scientific communities and his results strongly criticised.
Ampere learned about Orsted’s results in September 1820 and quickly developed the theory that would allow the emergence of electromagnetism. The success of this theory contributed to Orsted’s recognition, both in the scientific community and among his fellow citizens.