ELECTRICITY
The first precise experiments in
this field were carried out by Henry Cavendish at about 1771 and Charles Augustin de Coulomb in 1785. They demonstrated that the force acting
between two electric charges is very similar to the force of attraction between
two masses as described in
Especially important, however, is current electricity. We all know that electric current flows through metallic cables. The frog’s leg experiments carried out by Luigi Galvani in 1786 initiated detailed investigation into the phenomena of current electricity. In 1820 Christian Oersted discovered the magnetic field of electric current. By accurate measurement, Georg Simon Ohm found the basic relationships between voltage, current and resistance. The discovery made by Michael Faraday of the fact that the movement of a magnet relative to a conducting circuit produces an electric current (law of induction, 1831) revealed another link between electric and magnetic processes.
James Clerk Maxwell summarized the concepts of his time and widened them. The result was an admirable theoretical system of electrodynamics (after 1856) that comprised electric and magnetic phenomena. This theory was the basis for extensive conclusions. It anticipated the existence of electromagnetic waves, discovered by Heinrich Hertz in 1887-89. Today these are familiar to us in the form of radio and television. Experiments on electrical discharges in gases (beginning about 1869) supplied a key to one of the most profound secrets of nature- the structure of the atom.
Hertz’s Apparatus
In the years 1867-1889 Heinrich Hertz proved the existence
of free electromagnetic radiation. This
confirmed the theoretical system elaborated by J.C. Maxwell and laying the
foundation for electrical wireless communication.
by A. Brachner taken from-