Electricity is so present in our daily life which we often have tendency to regard it as a need of a natural nature, as well as running water. That sources of its production threaten to dry itself up and it is all the modern society which wavers. However, in comparison with the History, the use of the electric phenomena is relatively recent. studied as of end of XVIe century, electricity (within the meaning of the whole of the electric phenomena observable) remained a long time, for the general public, an object of curiosity and recreation, before them good progresses during last century do not show its practical utility. The extraordinary one penetration which it operated since in all the branches of the human activity,in particular by the means of electronics, is not foreign with efficiency that our contemporaries allot to the science.
Beginnings of electricity
Electricity and magnetism are two known physical phenomena since thousands of years. The theorization and the comprehension of the electric phenomenon are relatively recent, in comparison with very the long period of empirical applications, which it remains very often ignored.
High Antiquity with the Rebirth
The electricity term derives directly from the Greek word êlektron which indicates the yellow amber, a fossil resin having of the electrostatic properties. Same manner, the electromagnetic term refers to the magnesia stone, a natural magnet used as of High Antiquity (Magnesia is in the beginning a Greek city, now located at the west of Turkey).
These two roots indicate that the effects of electricity and magnetism were early discovered in the history of humanity. The lightning, natural magnetization, the static electricity of wool, are as many phenomena as the Men learned how to know and use.
At Hellènes, towards 600 av. J.C, Thalès de Milet see themselves allotting the paternity of the reflection on electricity, more precisely on static electricity and magnetism. However, only to the texts apocryphal books testify to its interest for these phenomena (it is Diogène Laërce, with the III esiècle, which brings back the remarks of Hérodote and Hypias on the Greek scientist). According to these texts, Thalès seemed to grant a heart to the things that one believed inanimate. Triboelectricity was already known, but could not be explained differently than by a vision animist of the matter, his physical properties being then inaccessible.
The use of magnetism in China
In China, the magnetic properties are used by the soothsayers starting from the II e and I er front century J.C, to manufacture magic tables of divinations. From there drift the first compass which indicates north, it is sophisticated after I er century of our era. The compass will be gradually used for construction and navigation. Moreover, one discovers under the dynasty Tang (618-907) the discordance between magnetic and geographical NORTH-SOUTH poles. Recovered by the Arabs, the compass arrives to Occident at the XI e century, that starts again the study of magnetism.
The use of the electricity produced by living beings
The electricity produced by living beings, in particular of electric fish, is also known since Antiquity. One finds for example low-reliefs of ancient Egypt representing of the electric catfishes. In addition, a mosaic of Pompéi represents a common torpedo. Scribonius Largus, under the reign of the emperor Claude Ier (41-54 after J.C.) described a treatment against the migraine or the drop which uses the electric shocks produced by a torpedo.
An experiment of Luigi Galvani with frog thighs put in contact with various metals, highlights a new phenomenon which will be the starting point of many developments of modern science, in what it opens the access to a broad use of electricity: its discovery of animal electricity.
The XVII e and XVIII e century : an historical turning point
To the XVI e century, William Gilbert, doctor of the Queen of England, gives the name of electricity to the phenomenon.
In 1733, the intendant Of Fay, examining the attraction and the repulsion of bodies electrified by friction, distinguishes a positive electricity and a negative electricity (resinous electricity, vitreous electricity).
In 1752, Benjamin Franklin shows that the lightning is a phenomenon due to electricity and invents the lightning conductor to be protected some.
In 1785, Charles of Coulomb presents a second memory to the Academy of Science, in which it exposes the law according to which the electrically charged bodies interact.
Static electricity: first discovered
The first research concerning electricity, before the advent of electromagnetism, will be focused on the electrostatic phenomena. With the electrical production by machines with friction can begin the first concrete experiments. Ramsden or Wimshurst which manufacture the first electrostatic generators, the discovery of the condensers, knowledge concerning the chemical, calorific and luminous properties of the electric current is specified.
XIX e century and electromagnetism
In 1820, Hans Christian orsted discovers the relation between electricity and magnetism, whose laws will be described by Andre-Marie Ampère, Michael Faraday, Jean-Baptiste Biot and Felix Savart, to be finally formatted by James Clerk Maxwell.
In 1831 Michael Faraday (1791-1867) discovers electromagnetic induction: the creation of a current in a driver starting from a magnetic field.
In 1832 Hippolyte Pixii, manufacturer of instruments of physics in Paris, produces the first electric machine with induction including/understanding a magnet turning opposite the poles of a fixed electromagnet. It is a generator of alternative course which makes it possible to obtain D.C. current thanks to the switch of Mr. Ampère (two half-rings fixed at the axis allowing the inversion of the polarity). It is already the starter of a commutator. Joseph Henry observes the spark occurring with the opening of an electrical circuit and names this phenomenon extracurrent of rupture. It is the discovery of the self-induction.
In 1833 Heinrich Lenz (1804-1865), Russian physicist of German origin, establishes the law which gives the direction of the induced current.
In 1865 James Clerk Maxwell publishes his treaty of electricity and magnetism, true base of modern electromagnetism. The famous Maxwell's equations are established.
In 1885 Galileo Ferraris, Italian engineer, introduced the principle of the spinning field pattern into the construction of the electrical motors.
In 1799, Alessandro Volta invents the battery by piling up different metal discs alternatively (copper, zinc) separated by felt discs soaked with acid.
Peter Barlow (1776-1862) built in 1822 what can be regarded as the first electrical motor of the history: the wheel of Barlow which is a simple metal disc cut out out of star and whose ends plunge in a cup containing of the mercury which ensures the arrival of the current.
Russian professor Hermann von Jacobi built in 1834 an engine of a power of one horsepower which will propel a paddle boat to paddles on Neva, in Saint-Pétersbourg. The inductor and the armature are electromagnets out of horseshoe carried by a mobile crown and a fixed crown in glance one of the other. The switch called gyrotrope opposite with the suitable positions the energization of the mobile electromagnets. But this engine is cumbersome and, finally, it is American Thomas Davenport who will be the true inventor of this kind of machine. One owes in Jacobi the concept of counter electromotive force.
Charles Grafton Page tries out an auto-transformer in 1835. The same year, Thomas Davenport, blacksmith with Brandon in Vermont in the United States, built one of the first electric vehicles. The electrical motor was probably an engine of the kind piston simple effect of engine.
Nicholas Joseph Callan realizes in 1837 the first transformer made up of a primary education and a secondary.
Charles Grafton Page builds in 1838 an induction coil which can be regarded as the ancestor of the reel of Ruhmkorff. Construction of an electrical motor similar to the piston simple effect of the steam engines, vapor being replaced by two electromagnets out of U.
1840 see the arrival of the electrical motor of Bourbouze. The pistons of a steam engine are replaced by alternatively excited electromagnets thanks to contacts ordered by a drawer distributer.
Gustave Wheat (1815-1865) built the first machine with variable reluctance in 1845. It is about a rotary engine comprising a crown of fixed electromagnets which attract iron bars carried by a wheel.
Heinrich Ruhmkorff develops in 1856 the reel which bears its name while being based on work of its predecessors and in fact a powerful scientific instrument that it markets.
Gaston Planté (1834-1889) invents in 1859 the accumulator or crushes reversible. The same year Antonio Pacinotti (1841-1912) develops an electric machine made up of a steel ring surrounded by a copper wire, the ring of Pacinotti. It is the base of the electrical motor and the dynamo.
Antonio Pacinotti publishes in 1865, in N O 19 of the review Nuovo Cimento, a communication on a ring turning in a magnetic field. This invention precedes the armature of the electric machines of which it considers the use as well out of generators as out of engines. Not having been able to exceed the experimental stage, its achievements remain without continuation.
The Wilde English realizes in 1868 the first dynamoelectric machine or dynamo. He replaces, following work of Werner von Siemens, the permanent magnet by an electromagnet supplied with an auxiliary machine.
In 1869, the Belgian inventor Zénobe Gram (1826-1901), born in Jehay-Bodegnée (province of Liege), makes possible the realization of the generators to D.C. current by imagining the collector. He improves the first antiquated versions of alternators (1867) and becomes famous by finding the principle of ring armature of Pacinotti. In 1871, it presents to the Academy of Science of Paris the first industrial generator of D.C. current, which one called machine of Gram and which was in fact a magneto.
Diffusion of electricity
In 1878, Thomas Alva Edison, American inventor, found Edison Electric Light Co. in New York. The following year, in 1879, it presents its first flashlight with incandescence (with carbon filaments) which remains lit 45 hours.
Always in 1879, a hydro-electric power station of 7 kw is built in Saint-Moritz. In the years 1880 Aristide Bergès promotes the concept of Hydro-electric power.
In 1881, France organizes, between on August 1st and on November 15th, an International exhibition of electricity which devotes the birth of the electrical engineering, underlined by an international Congress of the electricians which sits at Paris from September 15th to October 19th. The great innovation is the industrial employment of the Gram dynamo.
In 1882, Edison inaugurates the first electric factories (production of continuous tensions) built in London (Holborn Viaduct) and New York (Pearl Street: 110 V, 30 kw). A first test of transport of electrical energy is carried out this same year, by French Marcel Deprez in Germany. Of a 57 km length, this air line uses a telegraph wire since Miesbach, where a steam engine actuating is installed a Gram dynamo. The line supplies under 1.000 V a pump creating an artificial cascade with the exposure of Munich.
At the end of August 1883, Marcel Deprez carries out another experiment of electricity transmission between Vizille and Grenoble on a distance of 14 km, always in D.C. current. The market of the downtown area of Grenoble is thus lit by the electric light.
In 1883, Lucien Gaulard, young French electrician, chemist of formation, introduces to the French company electricians a secondary generator, called since transformer. In front of the skepticism of its compatriots, he addresses himself to the English John Dixon Gibbs and shows in London the cogency of his invention.
In September 1884, Lucien Gaulard and John Dixon Gibb position to obtain a price during the exposure of Turin and to thwart the opponents with the transport of the alternative course. They bring into service a buckled connection of demonstration (133 Hz) supplied with alternative course under 2.000 volts and making the return ticket of Turin at Lanzo (80 km). One ends then up admitting the advantage of the transformer, which makes it possible to raise the tension delivered by an alternator and thus facilitates the transport of electrical energy by lines with high voltage. The recognition of Gaulard will intervene too tardily because, meanwhile, of the patents were also taken by others. The first patent of Gaulard in 1882 was not even delivered in its time, under pretext which the inventor claimed to be able to do something of nothing! Gaulard tackles, loses its lawsuits, it is ruined and finishes its days in a lunatic asylum. The transformer of Gaulard of 1886 does not have great a deal to envy the current transformers, its closed magnetic circuit (the prototype of 1884 comprised an open magnetic circuit, from where a quite poor output) consists of an iron wire multitude announcing the laminated circuit with isolated sheets.
Thus, in 1885, the Hungarians Károly Zipernowsky, Miksa Déry and Otto Titus Bláthy develop a transformer with an annular core marketed in the whole world by the Ganz firm in Budapest. In the United States of America, William Stanley develops also transformers.
In Galileo Ferraris, Italian engineer, introduced the principle of the spinning field pattern into the construction of the electrical motors.
Production and distribution: the time of the engineers
Work of a great number of scientists between 1860 and 1890 led to the appearance of machines able to produce electrical energy in great quantity, like with the possibility of transferring it onto long distances.
The international conflicts of this time explain why it is difficult to allot to such or such person the paternity of an invention: scientists like Nikola Tesla or Lucien Gaulard which one is sure that they invented the machines with alternative course respectively and the transformer (essential components of the production and electric transport) died in misery, dispossessed of their patents by other financial much better engineers.
One can consider that the invention of the machine with D.C. current, patented by the Belgian Zénobe Gram must much with work of Italian Antonio Pacinotti and the German Ernst Werner von Siemens. Improved and marketed in the United States by Thomas Edison, his employment was defended in Europe by many engineers (of which Marcel Deprez) and the financial ones which had interest there. towards holding of the production and transport in alternative course, this powerful lobby made its possible to impose the D.C. current. Edison, for example, formally disadvised of it the use downtown because of a risk of electrocution by induction for the users of the telephone.
It is Lucien Gaulard and John Dixon Gibbs who, in 1883, succeed in the first transporting electrical energy on a distance of 40 km thanks to an alternative course generated under a tension of 2.000 volts. The transformer, invented by Gaulard, makes it possible to strongly increase the tension with the detriment of the intensity of the current and thus to enormously decrease the losses by Joule effect during transport at long distances.
In 1886 George Westinghouse, inventor and American industrialist born in Central Bridge (state of New York), is interested in industrial electricity and founds Westinghouse Electric Corporation. After having obtained in 1887 a patent for a transformer, it carries out in Buffalo a first network with alternative course for lighting. In the United States, it obtains towards Edison the contract of installation of all the electric infrastructure. Thus in the whole world the alternative course for the distribution of electricity is essential. This invention will make it possible to distribute energy in all the territory of the developed countries and to cause one second industrial revolution. Today its group became the number two American of the sector of the production of electrical material and electronics, behind General Electric.
In 1886, the City of Light of Bourganeuf into Hollow is the first in France, even in Europe, to inaugurate an electric lighting of the whole of the streets of the locality with a production site far away from the places of consumption.
In 1887 Nikola Tesla, Yugoslav electronics engineer born in Smiljan, in Croatia, founds a company for the construction of the alternators. Thanks to its work, the alternative course will gain the battle of remote transport and the use of the alternative course. Tesla recommends initially the use of the polyphase currents (1882) and succeeds in creating a turning magnetic field which makes it possible to rotate a revolving mobile reinforcement. In 1891, the first experiment for the transport of energy to large scales is made in Germany. It is the realization of a 175 kilometers long line enters Lauffen-on-the-Neckar and Francfort-sur-le-Main. And the output reached is already of 75%! He imagines in 1890 the first assembly producing a high frequency current. Tesla continues research tasks. One owes him the famous Tesla assembly in the field of radioelectricity but that does not prevent, in spite of other inventions, which it does not finish to him also its days in misery. One gave his name to the magnetic unit of induction in the system IF, the Tesla (symbol T).
The examination of the state of the art as published in the Dictionary of the electricity of R. Lefèvre (1895) watch very great creativity of this time concerning the uses of electricity, with many applications now disappeared like:
Michail Ossipowitsch Doliwo-Dobrowolski, Russian electrician, invent in 1889 the first asynchronous motor with three-phase current with squirrel-cage (built industrially as from 1891). In fact the asynchronous motor was in the air. This same year sees the startup of the first line of transport in alternative course in the United States: Oregon city - Portland cement. From a 21 km length, it feeds under 4 Kv.
The following stage consisted in characterising the electric force exerted by a charge carrier on another. The physicists did not have to go to seek well far : they took as a starting point the law of GRAVITATION of Newton stated one century before. They proposed a force proportional thus with the charge electric of each carrier in interaction, and inversely proportional squared of the distance which separates them. This law was checked in experiments in 1785 by the French Charles Augustin of Coulomb (the international unit of electric charge bears its name). Last bricks of the theory of the interactions between motionless electric charges were posed in the years which followed.Taking into account the strong similarity between the law of Coulomb and the law of gravitation, the formalism and the concepts of Mechanics were transported in the field of electrostatics. It is on this occasion that concept of POTENTIAL,introduced in 1772 per Joseph Louis de Lagrange for the gravitation, was taken again, in 1784, by Pierre Simon of Laplace to describe the electric state generated in an unspecified point of space by a whole of loads électriques.
It is at the time when the electrostatic theory became ripe which a shock wave came to shake. The revolution came from where it less was awaited: work of one Italian anatomist, Luigi Galvani, on the muscles of dissected frog thighs. In 1791, it discovered that these muscles expressed curious electric properties as soon as one put them in contact with two metals of different nature. To interpret these phenomena, it made a bringing together with a device developped at the point a few years before by the German Ewald Georg von Kleist: the bottle of Leyde. It was about a simple bottle with which the internal wall was covered with a metal sheet beforehand electrically charged, which discharged abruptly as soon as it was put in contact with a conductor (it constitutes the first electric capacitor for this reason). For Galvani, the frog constituted a natural Leyden jar, that the contact with two conducting metals was enough to discharge from its mysterious animal electricity. Skeptic, the Italian physicist Alessandro Volta took again the experiments of its compatriot and showed that the frog played only one secondary part: the electric effect resulted in fact from the establishment of contact between two metals of different nature via a wet fabric. Taking as a starting point this conclusion, it developed in 1800 the first accumulator, made up of a stacking (from where its name) of zinc and copper discs, between which fabrics soaked with acid were intercalated. This invention revolutionised electricity: contrary to the machines electrostatic that one was to charge by friction and who discharged in a very short time, the pile of Volta spontaneously produced, by chemical reaction, a kind of continuous discharge that the French physicist André Marie Ampère baptized in 1820 electric current. An electric current is anything else only one total displacement of loads within a conductor. In homage to Amp, the international unit of the intensity of the electric current, that is to say of quantity of loads which crosses a section of conductor per unit of time, bears the name of amp.In homage to Volta, the tension, that is to say the size which it introduced to measure the capacity of a pile to produce a current, expresses itself in volts. Thanks to this considerable lengthening time of discharge (increased by the realisation of increasingly powerful piles), it became possible to observe the effects of a long passage of current in a multitude of body. One was not long in realising only while plunging in water, or more generally in an aqueous solution, two solid stems connected at the boundaries of a pile (two electrodes, according to the terminology introduced by Michael Faraday a few years later), one caused the decomposition of the solution in his elementary components, that is to say electrolysis. This technique made it possible to the English chemist Humphry Davy to discover, at the beginning of XIXe century, a multitude of elements up to that point unknown: sodium, potassium, calcium, magnesium, barium and strontium. In substituent with the aqueous solution a gas enclosed in an enclosure out of glass, one carried out the first durable electric shocks, which were going to be used as a basis for first devices of urban lighting in second half of the XIXe century. Lastly, in 1841, the English James Prescott Joule observed that the passage of an electric current in a metal conductor caused an heat emission. It is the Joule effect, vital for irons with repasser
Magnetic effects of electricity
One second revolution occurred, in the north of Europe this time. In 1820, a professor of physics university of Copenhagen, Hans Christian OErsted, observed that a discussion thread traversed by one electric current deviated a magnetised needle placed in the vicinity. This experiment,in same time that it revealed for the first time the existence of magnetic effects electricity, inaugurated the study of the interactions between magnets and wire traversed by currents.This study had considerable theoretical implications. Thanks to work of Amp, it leads to assimilation of a MAGNET to a reel of discussion thread and the reduction of any phenomenon magnetic with an interaction between conducting wire.
It also showed that a magnet could move one discussion thread traversed by a current. Tie started from this effect to make turn an electrical circuit, Michael Faraday realised, since 1821, which can to be regarded as the ancestor of the electrical motor. It in did not remain there. Obsessed by the idea to highlight the reciprocal effect of that observed by Oersted, that is to say the possibility of generating an electric current thanks to magnetism, he managed to show, in 1831,an electric current appears spontaneously within a circuit when one moves a magnet with his vicinity (or, which returns with the same, when the surrounding magnetic field varies during time). This phenomenon, called electromagnetic induction, at the same time enabled him to produce the first generator, that is to say the first power source not functioning starting from a reaction chemical but coming from a movement mechanical and to design the first transformer, able to increase or decrease an electric tension. These three elements, the engine, the generator and the transformer, were going to become the three pillars of industry électrique.
Laws of the circuits
Second half of the XIX E century was marked by a double movement: while electricity industrial and its applications developed in a spectacular way, the physicists attempted to unify the whole of the phenomena observed by their predecessors. In this last field,a first decisive stage was reached in 1848 by the German Gustav Kirchhoff, who showed that phenomena associated with the electric currents, which constitute what one calls today the electrokinetic one, were of same natural that the electrostatic phenomena(on this occasion, the electric tension, size initially purely electrokinetic, were identified with the potential difference electrostatic). By doing this, it gave to the electrokinetic one the form that it has today and which is used as a basis for the study of the electrical circuits. It left its name to two fundamental laws. The first, as called law of the nodes, said as all the intensity which arrive in a node, that is to say in a point of junction of an electrical circuit, is equal with all that which in share. The second law, or law of the meshs, indicates that in a mesh, that is to say a branch of closed loop, the sum of the terminal voltages of the various elements of the mesh is overall null. These laws, when they are related to a good knowledge of the elements which constitute the circuit, give access the characteristics of this one (intensities traversing its various branches, terminal voltages of each element).
Unification of electricity and magnetism
The experiment of Oersted had highlighted the existence of links between electricity and magnetism.The two fields were unified by the Scot James Clerk Maxwell in 1864, giving rise to the éléctromagnétise. The principal consequence of this new theory was, from the point of view of electricity, the identification of the propagation velocity of the electric phenomena, which one had hitherto vainly tried to measure, with that of the light. It was not besides really about one new result, because Kirchhoff had already arrived, by a purely electrokinetic way,with such a conclusion seven years before, in the particular case of the study of the propagation of electrical signals along a telegraph wire (the equation which it reaches is known under the name of equation of the telegraphists).
Second half of the XIXe century was marked by a spectacular development of industrial, or electrotechnical electricity. The pile of Volta was supplanted soon by more powerful piles, as the pile Daniell (1836), the pile Bunsen (1841) or crushes it Leclanché (1864). In 1859, Gaston Planté developed the first rechargeable accumulator,or accumulator. The generators made similar great strides: the invention of the dynamo in the years 1870 by Zénobe Gramme preceded the appearance of the first generators of alternative courses, or alternators, in particular thanks to work of Croatian engineer Nikola Tesla (which left its name to the unit international of the magnetic field). These devices, driven by the immense turbines of the power stations electric (that they are thermal, hydroelectric or nuclear) constitute the element exchange of the production of electrical energy. The development of the generators accompanied enough naturally that the devices opposite, namely the electrical motors. This progress contributed with the development of the applications of electricity throughout last century. Since 1839 appeared in England the first instrument of telecommunication functioning using electrical signals transmitted along a wire, the telegraph, developed by engineers William Cooke and Charles Wheatstone.
In 1876, electrical signals for the first time were used by the American Graham Beautiful to transport the human voice remotely: the telephone had been born. Soon, it was with the turn of the electrified to be means of transport: the first electric tram of the engineers German Werner von Siemens and Johann Halske goes back to 1879 the first electric train, invented by Thomas Edison, date of 1880. Thanks to the development of the electric transformers in the years 1880 and with the high voltages which these devices made it possible to obtain, it became possible to extend the haul electricity since its place of production to the heart of the cities (electric losses caused by the Joule effect along a line are all the more weak as the tension of the line is high).The demonstration more striking this penetration was certainly the rise of urban lighting,licence by the recent tuning by Edison of a new type of lamp, the incandescent lamp (resting on the emission of an intense visible radiation by a refractory material wire brought to high temperature by Joule effect).
Carriers of electricity
The quick change of electrical engineering to the XIX E century proves that it was not need to know the nature of the electric charge carriers to use their properties. This one was not elucidated that at the end of the XIXe century and at the beginning of the XXe century thanks to the discovery of the electron and the atomic structure of the matter (see ATOM). From these discoveries, it came out that the electric phenomena did not result from a mysterious electric fluid independent of the matter, only one had vainly tried to characterise centuries during, but of the structure same of the matter, intrinsically electric since two of the three elementary components of the atom (the electron and the proton) are carrying an electric charge. Much more, it proved that this electric character as well explain the cohesion of the atom, that of the Molecule and that of the SOLID.
As for the electric current, its nature depends above all on the physical status considered. In a metal solid, it result only from the displacement of the electrons related to the crystal structure, or electrons of conduction (in a semiconductor, the things are a little more complicated, to see SEMI-CONDUCTIVITé). A zone of a solid can thus appear positively charged only by deficit with electrons.In a LIQUID, the electric current is ensured thanks to the presence preliminary and to displacement of IONS (that is to say of atoms which lost or gained electrons) within fluid, ions charged positively (or cations) moving in opposite direction with the ions charged negatively (or anions). In a GAS, finally, where all particles, that they are atoms or of molecules, are initially neutral, the things happen in two times: the application of a tension electric between two electrodes ionisation partial of gas causes, in other words the scission of the particles in positive ions and electrons (it does not act then any more with strictly speaking about a gas, but about what one calls a PLASMA).It is the consecutive movement of the particles charged towards the electrodes which constitutes the current électrique.
An electrical communication being composed of consumption and production machine tools, as well as structures (lines, transformers) to connect them, the electrical communications appeared only towards end XIX e century, when each element had reached a sufficient technological maturity.
First networks acourant continuous
Edison at summer a pioneer in the realization of the first electrical communications in D.C. current.
At the time of first half of the XIX e century, the inventors develop acourant of many types of electrical motors continuous, but their use in an industrial way serà allowed only after the invention of the dynamo (generating of D.C. current) by Zénobe Gram in 1869, which serà quickly improved. to the International exhibition of electricity of Paris of 1881, Marcel Deprez presents for the first time an electric installation of energy distribution supplied with 2 dynamos. with the autumn 1882, the first electrical communications appear simultaneously anew York and Bellegarde, in France. They are very local and use the D.C. current.
Thomas Edison with played a determining role in the development of electricity : it founds in 1878 Edison Electric light Co which deviendrà in 1892 General Electric, deposits the patent of the electric bulb in 1879, then creates the electrical communication of New York. This last, the purpose of which was primarily lighting, develops quickly: from a power of 1200 bulbs in 1882, it passes to 10000 bulbs the following year.
This network, which suffers from many breakdowns, is made up small powerplants (30 kw) and of a distribution network with 110 V. It however is very limited because the routing of electricity is not possible that on a few kilometers.
acette period the first experiments of transport of electrical energy develop and are carried out in particular by Marcel Deprez, who uses D.C. current. They are however relative failures because they do not allow the transport of industrial powers (Deprez successful in 1882 to transport 400 W out of 57 km of distance, but with a total output from only 30%. Engineers Lucien Gaulard and John Gibbs work as for them on the alternative course. Although the transformer is known since 1837, they develop in 1884 a using transformer of strong power of the three-phase alternative course, which makes it possible to change the level of tension easily. the same year they show the advantage of the transformer by bringing into service a 80 km length line fed in alternative course under 2.000 V.
victory of the three-phase alternative course
Tesla, an inventor who with conceived the first electrical communications in alternative course
George Westinghouse, engineer and American contractor who with created his own company of electricity, is interested by the technology of the alternative course. In 1887, it buys the patents of the transformer of Gaulard and recruiting Nikola Tesla which invents the three-phase alternator in 1891. This same year the first three-phase installation is installation around Frankfurt, with a line of 175 km.
in the United States the networks in D.C. current continue their development, but are limited in the face: each power station can feed in electricity only one zone approximately 5 km in diameter, which poses problem apart from the cities. In parallel small urban networks in alternative course are constituted. A severe opposition makes rage acette time in the United States between Edison (defender of the D.C. current) and George Westinghouse with Tesla (defender of the alternative course). Edison insists in particular on the risk of the alternative course in high voltage for the living beings, going until organizing public demonstrations where it electrocutes various animals, to prove the dangerosity of the alternative course, and và until financing the macabre invention of the electric chair. after the execution of William Kemmler, Edison dirà: It at Westinghouse summer.
the decisive battle between D.C. current and alternative proceeds around a project of power supply of the industry of Buffalo by a hydro-electric power station of 75 MW located at Niagarà Falls, 32 away km. Edison proposed a project in D.C. current while Tesla and Westinghouse proposed a system in alternative course. The contract was given to Westinghouse. In 1896, the startup of the first industrial line in three-phase current was a total success and conduit for at least one century aimposer universally the three-phase alternative course like means of transport of electrical energy, better adapted acette time to transport on long distances.
The Leyden jar is the ancestor of the condenser. It was carried out the first time in 1745 in the town of Leyde in the Netherlands by Pieter van Musschenbroek.
The first application of this condenser was to give commotions to the public in the fairs. For example, to Versailles, one presented to the king Louis XV the experiment of the discharge of a large Leyden jar through the circuit formed of more than two hundred courtiers.
The Leyden jar is a formed condenser of two drivers separated by glass from the bottle. The first driver generally consists of a higher electrode, connected by a small chain to sheets out of tin crumpled contained in the bottle. The second driver is formed by a metal sheet wrapping the bottle. The interior and external faces store an equal electric charge but of opposite sign.
The original bottle consisted of a bottle out of glass covered with a sheeting metal and accidentally containing impure water acting like a driver, connected by a chain to a metal sphere. The initial assumption was that electricity was stored in water. It was discovered then that the loads accumulate on surfaces in opposite, separated by glass, forming dielectric and that the liquid could be replaced by metal sheets connected to the electrode by a conducting stem. The loads are stored on the surface of the elements, at the border with the dielectric one. More the dielectric one is fine and thus more space between the plates is mean, plus the cumulable load with a given tension is important.
The development of the condensers revealed that the materials of dielectric are not critical but could influence the electric capacity and limit the electric arcs between the plates, tension of breakdown. Two plates separated by a weak interval act like a condenser, even in the vacuum.
Initially, the measuring unit of the capacity was the bottle, about equivalent to 1 nF.
The Greeks of Antiquity employed amber balls which they rubbed to produce of the sparks. It is the effect triboelectric, mechanical separation of load in dielectric. Their work was necessary to the development of the Leyden jar.
About 1650, Otto von Guericke built a primitive generator with friction: a ball of sulfur turning at high speed on an axis. When Guericke posed its hand on the ball and turned the axis quickly, a load of static electricity accumulated. In 1745, another German, Ewald von Kleist, found a method to store this load. It rolled up a silver foil around a bottle out of glass, and charged the sheet using a generator with friction. Kleist convainquit that a substantial load could be accumulated when it accepted a significant electric shock. This invention remained under the name of Leyden jar because in 1746, Pieter van Musschenbroek, professor of the university of Leyde, made independently the same discovery and made known it with the scientific world. Musschenbrœk thus describes its experiment in a letter of April 20th, 1746, addressed to Réaumur.