The French physicist and mathematicisn André-Marie Ampère (1775-1836) discovered many of the laws governing the relationship between electricity and magnetism (1820). Ampere found that when electricity flows through a coiled wire, it becomes a magnet. He found that two parallel current wires will repel or attract each other, depending on the direction of the current. Ampere also discovered that electrons move through conductors, that electrons flow away from a negative charge (the cathode) and towards a positive charge (the anode). Ampere invented the astatic needle, which measured and detected electrical currents (and led to the invention of the Galvanometer). Using his astatic needle, Ampere showed that an electric current makes a circuit travelling through a battery.

The ampere or amp, the unit of the rate of flow of an electrical current was named for Ampere.