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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Electric lamp. History of invention and production
Directory / The history of technology, technology, objects around us An incandescent lamp is an artificial light source in which light is emitted by an incandescent body heated by an electric current to a high temperature. As a heating body, a spiral made of refractory metal (most often tungsten) or a carbon filament is most often used. To prevent oxidation of the heating body upon contact with air, it is placed in an evacuated flask, or a flask filled with inert gases or halogen vapors.
In the last decades of the XNUMXth century, electric lighting entered the life of many European cities. Appearing first on the streets and squares, it very soon penetrated into every house, into every apartment and became an integral part of the life of every civilized person. It was one of the most important events in the history of technology, with enormous and manifold consequences. The rapid development of electric lighting led to mass electrification, a revolution in energy and major shifts in industry. However, all this might not have happened if the efforts of many inventors had not created such a common and familiar device for us as an electric light bulb. Among the greatest discoveries of human history, she undoubtedly belongs to one of the most honorable places. In the XNUMXth century, two types of electric lamps became widespread: incandescent and arc lamps. Arc light bulbs appeared a little earlier. Their glow is based on such an interesting phenomenon as the voltaic arc. If you take two wires, connect them to a sufficiently strong current source, connect them, and then push them a few millimeters apart, then something like a flame with a bright light is formed between the ends of the conductors. The phenomenon will be more beautiful and brighter if two pointed carbon rods are used instead of metal wires. With a sufficiently large voltage between them, a light of dazzling power is formed.
For the first time, the phenomenon of a voltaic arc was observed in 1803 by the Russian scientist Vasily Petrov. In 1810, the English physicist Devi made the same discovery. Both of them obtained a voltaic arc, using a large battery of cells, between the ends of charcoal rods. Both of them wrote that the voltaic arc can be used for lighting purposes. But first it was necessary to find a more suitable material for the electrodes, since the charcoal rods burned out in a few minutes and were of little use for practical use. Arc lamps had another inconvenience - as the electrodes burned out, it was necessary to constantly move them towards each other. As soon as the distance between them exceeded a certain permissible minimum, the light of the lamp became uneven, it began to flicker and went out. Foucault, a French physicist, designed the first manually adjustable arc lamp in 1844. He replaced charcoal with hard coke sticks. In 1848, he first used an arc lamp to illuminate one of the Parisian squares. It was a short and very expensive experience, since a powerful battery served as a source of electricity. Then various devices were invented, controlled by a clockwork, which automatically shifted the electrodes as they burned. It is clear that from the point of view of practical use, it was desirable to have a lamp that was not complicated by additional mechanisms. But was it possible to do without them? It turned out that yes. If two coals are placed not opposite each other, but in parallel, moreover, so that an arc can form only between their two ends, then with this device the distance between the ends of the coals is always kept unchanged. The design of such a lamp seems very simple, but its creation required great ingenuity. It was invented in 1876 by the Russian electrical engineer Yablochkov, who worked in Paris in the workshop of Academician Breguet. The Yablochkov candle consisted of two rods made of dense rotary coal, arranged in parallel and separated by a plaster plate. The latter played a dual role, since it served both to fasten the coals together and to isolate them, allowing the voltaic arc to form only between the upper ends of the coals. As the coals burned from above, the gypsum plate melted and evaporated, so that the tips of the coals always protruded a few millimeters above the plate.
Yablochkov's candles attracted everyone's attention and made a lot of noise. In 1877, with their help, street electricity was first installed on the Avenue de L'Opera in Paris. The World Exhibition, which opened the following year, gave many electrical engineers the opportunity to get acquainted with this wonderful invention. Under the name "Russian Light", Yablochkov's candles were later used for street lighting in many cities around the world. These lamps are also curious in that they required exclusively alternating current for themselves, since the rate of combustion of the positive and negative electrodes in them was not the same, and with direct current it was necessary to make the positive electrode thicker.
It was for Yablochkov that Gramm made his first alternator. But along with the advantages of Yablochkov's candles, they had their drawbacks. The main inconvenience was that the coals in them burned out very quickly - a medium-sized candle shone for no more than two hours. This disadvantage, however, was inherent in many other arc lamps. More than once, the inventors had the idea to enclose the voltaic arc in an atmosphere devoid of oxygen. After all, thanks to this, the lamp could burn much longer. For a long time, these attempts failed, as they tried to pump out the entire air from the entire lamp. The American Jandus was the first to come up with the idea of placing not the entire lamp under the dome, but only its electrodes. When a voltaic arc occurred, the oxygen contained in the vessel quickly reacted with hot carbon, so that a neutral atmosphere soon formed inside the vessel. Although oxygen continued to flow through the gaps, its influence was greatly weakened, and such a lamp could burn continuously for about 200 hours.
But even in such an improved form, arc lamps could not be widely used. The voltaic arc is a very strong light source. The brightness of its burning cannot be reduced below a certain limit. Therefore, arc lamps were used to illuminate large halls, stations or squares. But they were completely unsuitable for use in small living or working spaces. Incandescent bulbs were much more convenient in this sense. Everyone knows their device: an electric current, passing through a thin thread, heats it up to a high temperature, due to which it begins to glow brightly. Back in 1820, the French scientist Delarue made the first such lamp, in which platinum wire served as an incandescent body. After that, for half a century, incandescent lamps were hardly used, because they could not find a suitable material for the filament. At first, coal seemed to be the most convenient. In 1873, the Russian electrical engineer Lodygin made a light bulb with a filament from rotary coal. He was the first to start pumping air out of the balloon. In the end, he succeeded in creating the first incandescent light bulb, which received some practical use, but it was still very imperfect. In 1878, American electrical engineers Sawyer and Man found a way to make small carbon arcs of small cross section by charring cardboard in graphite powder. These arcs were enclosed in glass caps. However, these bulbs were very short-lived.
In 1879, the famous American inventor Edison took up the improvement of the electric light bulb. He understood that in order for the light bulb to shine brightly and for a long time and have an even unblinking light, it is necessary, firstly, to find a suitable material for the thread, and, secondly, to learn how to create a very rarefied space in the balloon. A lot of experiments were done with various materials, which were set up with Edison's characteristic scope. It is estimated that his assistants tested at least 6000 different substances and compounds, while over 100 thousand dollars were spent on experiments. At first, Edison replaced the brittle paper charcoal with a more durable one made from coal, then he began to experiment with various metals, and finally settled on a thread of charred bamboo fibers. In the same year, in the presence of three thousand people, Edison publicly demonstrated his electric light bulbs, illuminating his house, laboratory and several adjacent streets with them. It was the first long life light bulb suitable for mass production.
Since the manufacture of threads from bamboo turned out to be quite expensive, Edison developed a new method for dressing them from specially processed cotton fibers. First, cotton was placed in a hot zinc-chlorine solution, where it gradually dissolved. The resulting liquid was thickened with a pump to a paste-like state and squeezed out through a thin tube into a vessel with alcohol. Here it turned into a thin thread and wound on a drum. The resulting thread was freed from the chlorine-zinc solution by several intermediate operations, dried, cut, enclosed in v-shapes and charred in an oven without air access. Then a thin layer of coal was sprayed onto the filaments. To do this, they were placed under a cap filled with lighting gas, and a current was passed through them. Under the action of current, the gas decomposed, and a thin layer of carbon was deposited on the filament. After all these complex operations, the thread was ready for use. The process of making a light bulb was also very complicated. The thread was placed in a glass cap between two platinum electrodes fused into glass (expensive platinum had to be used because it had the same coefficient of thermal expansion as glass, which was very important for creating tightness). Finally, with the help of a mercury pump, the air was pumped out of the bulb, so that no more than one billionth of the air that it contained at normal pressure remained in it. When the pumping out was over, the light bulb was soldered and put on a base with contacts for screwing into the cartridge (both the cartridge and the base, as well as many other elements of electric lighting that have survived unchanged to this day - switches, fuses, electric meters and much more - were also invented by Edison). The average life of an Edison light bulb was 800-1000 hours of continuous burning. For almost thirty years, light bulbs were made in the manner described above, but the future was with light bulbs with a metal filament. Back in 1890, Lodygin came up with the idea to replace the carbon filament with a metal wire made of refractory tungsten, which had an incandescent temperature of 3385 degrees. However, the industrial production of such light bulbs began only in the XNUMXth century. Author: Ryzhov K.V.
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