Andre Marie Ampere, a French mathematician who devoted himself to the study of electricity and magnetism, was the first to explain the electrodynamic theory. A permanent memorial to Ampere is the use of his name for the unit of electric current.

George Simon Ohm, a German mathematician and physicist, was a college teacher in Cologne when in 1827 he published, “The galvanic Circuit Investigated Mathematically”. His theories were coldly received by German scientists but his research was recognized in Britain and he was awarded the Copley Medal in 1841. His name has been given to the unit of electrical resistance, the ohm.

Thomson had measured the ratio of the electron’s charge to its mass.
Then in 1899 he inferred a value for the electronic charge itself by observing the behavior of a cloud of tiny charged water droplets in an electric field. This observation led to Millikan’s famous Oil-Drop Experiment. Robert MILLIKAN, a physicist at the University of Chicago , with the assistance of his student Harvey Fletcher, sought to measure the charge of a single electron, an ambitious goal in 1906. A tiny droplet of oil with an excess of a few electrons was formed by forcing the liquid through a device similar to a perfume atomizer. The drop was then, in effect, suspended, with an electric field attracting it up and the force of gravity pulling it down. By determining the mass of the oil drop and the value of the electric field, the charge on the drop was calculated. The result: the electron charge -e- is negative and has the value e = 1.60/10,000,000,000,000,000,000 coulombs.