Physics

Electricity History


It was discovered by a Greek philosopher named Tales of Miletus who, rubbing an amber on a piece of sheepskin, noticed that pieces of straw and wood fragments began to be attracted to the amber itself.

From amber (gr. Élektron) came the name electricity. In the seventeenth century systematic studies on friction electrification were initiated, thanks to Otto von Guericke. In 1672, Otto invented an electric charge generating machine where a sulfur sphere constantly rotates by rubbing on dry land. Half a century later, Stephen Gray makes the first distinction between conductors and electrical insulators.

During the eighteenth century electric machines evolved into a rotating glass disc that is rubbed against a suitable insulator. An important discovery was the condenser, independently discovered by Ewald Georg von Kleist and Petrus van Musschenbroek. The capacitor consisted of an electrical charge storage machine. They were two conductive bodies separated by a thin insulator.

But an important invention of practical use was the lightning rod made by Benjamin Franklin. He said the electrification of two rubbed bodies was the lack of one of two types of electricity in one of the bodies. These two types of electricity were called resinous and glassy electricity.

In the eighteenth century the famous experiment of Luigi Aloisio Galvani was made in which electric potentials produced contractions in the leg of a dead frog. This difference was attributed by Alessandro Volta when making contact between two metals the leg of another dead frog. This experiment was attributed to his invention called the voltaic cell. It consisted of a series of altered copper and zinc discs, separated by pieces of cardboard soaked in salt water.

With this invention, a stable source of electric current was first obtained. Therefore, the investigations on the electric current increased more and more.

After a while, water decomposition experiments are done. In 1802, Humphry Davy electronically separates sodium and potassium.

Even with Volta's fame, more efficient batteries were created. John Frederic Daniell invented them in 1836 at the same time as Georges Leclanché's batteries and the Raymond-Louis-Gaston Planté rechargeable battery.

Physicist Hans Christian Örsted observes that an electric current acts on the needle of a compass. With this, it is clear that there is a connection between magnetism and electricity.

In 1831, Michael Faraday discovers that the variation in the intensity of the electric current traveling through a closed circuit induces a current in a nearby coil. An induced current is also observed by introducing a magnet into this coil. This magnetic induction had immediate application in the generation of electric currents. A coil next to a rotating magnet is an example of an alternating current generator.

The generators were perfected until they became the main sources of electricity supply mainly used in lighting.

In 1875 a generator is installed in Gare du Nord, Paris, to turn on the arc lamps of the station. Steam engines were made to drive the generators, and by stimulating the invention of steam turbines and turbines for using hydropower. The first hydroelectric dam was installed in 1886 near the Niagara Falls.

For power distribution to occur, iron conductors were initially created, then copper conductors and finally, by 1850, the wires covered by an insulating layer of vulcanized gutta-percha, or a layer of cloth, were already manufactured.

The publication of James Clerk Maxwell's Treatise on Electricity and Magnetism in 1873 represents a breakthrough in the study of electromagnetism. Light is now extended as an electromagnetic wave, one where it consists of electric and magnetic fields perpendicular to the direction of their propagation.

Heinrich Hertz, in his experiments from 1885, studies the properties of electromagnetic waveforms generated by an induction coil; In these experiments he observes that if reflected, refracted and polarized, just as light. Hertz's work shows that the radio and light waves are both electromagnetic waves, thus confirming Maxwell's theories; Radio waves and light waves differ only in their frequency.

Hertz did not explore the practical possibilities opened by his experiences; more than ten years pass, until Guglielmo Marconi uses radio waves on his wireless telegraph. The first radio message is transmitted across the Atlantic in 1901. All of these experiments have opened new avenues for the progressive use of electrical phenomena without virtually all of man's activities.

Source: www.mundociencia.com.br