André-Marie Ampère
Ampere is most known for establishing the relationship between electricity and magnetism, and combining them into a new field called electromagnetism, or electrodynamics. On September 11, 1820, Ampere heard from the discovery of H.C.Orsted that a magnetic needle can be activated by a voltaic current. Only a week later, he came up with a much more advanced version of that kindred phenomena. It was such an amazing development. On the same day, he also discovered like charges repel and different charges come towards each other.