Technical text: Electricity
Electricity (History)
The first machine for producing an electric charge was described in 1672 by the German physicist Otto von Guericke. It consisted of a sulfur sphere turned by a crank on which a charge was induced when the hand was held against it.
The French scientist Charles Fransois de Cisternay Du Fay was the first to make clear the two different types of electric charge: positive and negative.
Benjamin Franklin spent much time in electrical research. His famous kite experiment proved that the atmospheric electricity that causes the phenomena of lightning and thunder is identical with the electrostatic charge on a Leyden jar.
The British chemist Joseph Priestley proved the law that the force between electric charges varies inversely with the square of the distance between the charges experimentally in 1766. Priestley also demonstrated that an electric charge distributes itself uniformly over the surface of a hollow metal sphere, and that no charge and no electric field of force exists within such a sphere.
Charles Augustin de Coulomb invented a torsion balance to measure accurately the force exerted by electrical charges. With this apparatus he confirmed Priestley's observations and showed that the force between two charges is also proportional to the product of the individual charges. Faraday, who made many contributions to the study of electricity in the early 19th century, was also responsible for the theory of electric lines of force.
The Italian physicists Luigi Galvani and Alessandro Volta conducted the first important experiments in electrical currents. Galvani produced muscle contraction in the legs of frogs by applying an electric current to them.
The Danish scientist Hans Christian Oersted demonstrated the fact that a magnetic field exists around an electric current flow in 1819. In 1831 Faraday proved that a current flowing in a coil of wire could induce electromagnetically a current in a nearby coil. About 1840 James Prescott Joule and the German scientist Hermann Ludwig Ferdinand von Helmholtz demonstrated that electric circuits obey the law of the conservation of energy and that electricity is a form of energy.
An important contribution to the study of electricity in the 19th century was the work of the British mathematical physicist James Clerk Maxwell, who investigated the properties of electromagnetic waves and light and developed the theory that the two are identical. His work paved the way for the German physicist Heinrich Rudolf Hertz, who produced and detected electric waves in the atmosphere in 1886.
The Dutch physicist Hendrik Antoon Lorentz first advanced the electron theory, which is the basis of modern electrical theory in 1892. The widespread use of electricity as a source of power is largely due to the work of such pioneering American engineers and inventors as Thomas Alva Edison, Nikola Tesla, and Charles Proteus Steinmetz.