AndrÃ - Marie AmpÃ re ( January 20 , 1775 â `` June 10 , 1836 ) was a French physicist and mathematician who helped discover electromagnetism . AndrÃ - Marie AmpÃ re ( 20 January 1775 â `` 10 June 1836 ) was a French physicist and mathematician who is generally regarded as one of the main discoverers of electromagnetism .