Static electricity was observed by Thales, a Greek philosopher who lived in the sixth century B. C. He thought static electricity was a form of magnetism, and it was not until 1600 that electricity was recognized as something different from magnetism. This discovery was made by William Gilbert, an English physician. He called the force involved “electric,”; taken from elektron, the Greek word for amber. (Static electricity was first observed in amber.)

In the mid-1700's, E. Georg von Kleist of Prussia and Pieter van Musschenbroek of Holland, working independently, invented a device for storing electricity. In 1780 Luigi Galvani, an Italian physiologist, found that a severed frog's leg hung by a copper hook would twitch when touched with iron. Galvani had discovered current electricity (which for many years was called galvanism). Another Italian, Alessandro Volta, used Galvani's discovery when he invented the first electric battery in 1800. His studies led to the discovery of electrolysis, the decomposition of a substance with an electric current.

In his kite experiment of 1752 Benjamin Franklin proved that lightning is an electrical discharge. He suggested, incorrectly, that electricity is a kind of fluid and that it flows from a point where there is a surplus, or positive amount, to a point where there is a deficiency, or negative amount. This theory, called the conventional (or fluid) theory of current, persisted even after the development of the electron theory early in the 20th century. Today, the direction of a current is still considered to be from the positive terminal to the negative, even though electrons flow in the opposite direction.

In 1820, Hans Christian Oersted, a Danish physicist, discovered that an electric current can produce magnetic effects. In 1831 Michael Faraday, an English physicist and chemist, discovered the complementary phenomenon: that a magnet can produce electrical effects. (Joseph Henry, a United States physicist, observed the phenomenon in 1830 but did not publish his findings until after Faraday.) Faraday used this discovery—electromagnetic induction—to invent an experimental electric generator. He also formulated the laws of electrolysis and developed the first transformer.

Between 1870 and 1880, Sir William Crookes, an English scientist, experimenting with vacuum tubes, concluded that the rays produced in these tubes were composed of particles smaller than atoms. J. J. Thomson, an English physicist, demonstrated the existence of these particles (later called electrons) in 1897. Thomson's work led to the theory of electric current being the flow of electrons.

As the basic principles of electricity were discovered and electrical theories were developed, inventors began putting them to use. Among the electrical inventions of the late 19th century are Samuel F. B. Morse's telegraph; Alexander Graham Bell's telephone; Thomas A. Edison's electric light; Guglielmo Marconi's wireless telegraph; and electric generators and motors.

By the 1920's, scientists studying the electrical structure of the atom had developed a complex mathematical description of its nature. On a more practical level, the development during the early 20th century of such electrical appliances as electric refrigerators and washing machines helped raise the standard of living in many countries.

The understanding of the behavior of electrons in a vacuum permitted the development of electronics in the first half of the 20th century. Following the invention of the transistor in 1948, the use of electronic devices based on semiconductors came to dominate the field of electronics. The miniaturization of electronic devices led to the development of a large number of new electrical devices, such as the personal computer, and to the widespread use of electronic controls.