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Light bulb


Light bulb
In the last decades of the XIX century in the lives of many European cities included electric lighting. Appearing first on the streets and squares, it very soon penetrated into every home, in every apartment, and became an integral part of the life of every civilized man. It was one of the most important events in the history of art, which had enormous and diverse effects. The rapid development of electric lighting led to mass electrification, upheaval in the energy sector and a major shift in the industry. However, all this could not happen if the efforts of many inventors have not been established is usual and customary for our device, like a light bulb. Among the greatest discoveries in human history it undoubtedly belongs to one of the most honorable places.

In the XIX century have proliferated two types of light bulbs: incandescent and arc. Arc bulb appeared a little earlier. Glow them based on such an interesting phenomenon of the voltaic arc. If we take the two wires, connect them to a strong enough power source, connect, and then move apart at a distance of a few millimeters, between the ends of the conductors formed something like a flame with a bright light. The phenomenon will be more beautiful and brighter, if instead of metal wires take two sharpened carbon rod. When a sufficiently large voltage is formed between the light blinding force.

For the first time the phenomenon of electric arc observed in 1803 Russian scientist Vasily Petrov. In 1810, the same discovery made British physicist Devi. Both of them got voltaic arc, using a large battery of elements between the ends of the rod-charcoal. And he and the other 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 because of burned charcoal bars for a few minutes and were unsuitable for practical use. Arc lamps have both an inconvenience - as burnout of the electrodes had to constantly move them toward each other. As soon as the distance between them is greater than a permissible minimum lamp light grew uneven, she began to flicker and dim.

The first arc lamp with manual adjustment of the arc length constructed in 1844 by French physicist Foucault. Charcoal he replaced the sticks of hard coke. In 1848, he was the first to use an arc lamp to illuminate one of the Paris area. It was a short and very expensive experience, as the source of electricity is a powerful battery. Then it was invented various devices operated by a clockwork mechanism, which automatically moved the electrodes as they are burning.

It is clear that from the standpoint of practical use, it is desirable to have the lamp was not complicated by additional mechanisms. But can we do without them? It turns out that, yes. If you put two coals are not against each other, and in parallel, in such a way that the arc could be formed only between the two ends thereof, that in this case, the distance between the ends of coal always remains unchanged. The design of this lamp looks very simple, but its creation has required great ingenuity. It was invented in 1876 by Russian Yablochkov electrician who worked in Paris in the studio academician Breguet.

Candle Yablochkov consisted of two rods made of dense carbon rotary arranged in parallel and separated by a plaster plate. The latter played a dual role, as it serves to bond and coal between themselves and for their isolation, allowing the voltaic arc formed only between the upper ends of the coals. As the coal burns on top of gypsum plate melts and evaporates, so that the tips of the coals are always a few millimeters were on the record.

Yablochkov Candles attracted worldwide attention and made a lot of noise. In 1877, with their help, it was arranged for the first time on the street Electricity Avenue de L'Opera, Paris. World's Fair, which opened the following year, provided an opportunity to many electricians acquainted with this remarkable invention. Under the title "Russian light" candles Yablochkov later used for street lighting in many cities around the world. These lamps are curious by the fact that the demand for itself exclusively the AC, as the rate of combustion of the positive and negative electrodes in them was different and at a constant current was necessary to do the positive electrode thickness. It is for Yablochkov Gram produced his first AC generator. But along with the advantages Yablochkov candles had their drawbacks. The main inconvenience is that coals are burned very quickly - the average value of the candle lights are not more than two hours.

This drawback, however, was also characteristic of many other arc lamps. Not once have been thought inventors conclude voltaic arc in an atmosphere devoid of oxygen. Indeed, thanks to this lamp would burn for much longer. For a long time these attempts were not successful, since trying to deflate the air completely out of the entire lamp. American Dzhandus first came up to put a dome lamp is not all, but only its electrodes. When an electric arc oxygen enclosed in a vessel, quickly react with the hot carbon so formed inside the vessel shortly neutral atmosphere. Although oxygen and continues to flow through the gaps, its influence is strongly attenuated, and the lamp is able to continuously burn about 200 hours.

But even in this improved form arc lamps could not get enough widespread. Voltaic arc is a very strong light source. The brightness of her burning can not be reduced below a certain limit. Therefore, arc lamps were used to illuminate large halls, railway stations or areas. But they were totally unsuitable for use in residential or small workplaces.

It is much more convenient in this respect are incandescent bulbs. The device we all know them: an electric current passing through a thin filament, it heats to a high temperature, so that it begins to glow brightly. Even in 1820, a French scientist Delarue made the first of a lamp in which an incandescent body served as a platinum wire. Thereafter, for half a century incandescent lamp hardly been used because they could not find a suitable material for the thread. At first it seemed the most convenient coal. In 1873, the Russian electrician Lodygin made a light bulb with a filament of rotary coal. He first began to pump air from the balloon. In the end he managed to create the first incandescent light bulb, get some practical use, but it was still very imperfect. In 1878, the US electrical Sawyer and Man found a way to produce small carbon arc small section by charring cardboard graphite powder. These arc encased in glass capsules. However, these bulbs were very short-lived.

In 1879, for the improvement of the light bulb took the famous American inventor Edison. He understood that in order to shine a bright light for a long time and had a smooth non-flashing light, it is necessary, first, to find the right material for the filament, and, secondly, to learn how to create a cylinder of highly rarefied space. It has been done many experiments with different materials, which were placed with characteristic scale for Edison. It is estimated that his aides tried no less than 6000 different substances and compounds, and the experiments have been spent on more than 100 thousand dollars. First Edison replaced the brittle paper ember more durable, made from coal, and then began to do experiments with different metals and finally settled on a thread of the charred bamboo fibers. In the same year in the presence of three thousand people Edison publicly demonstrated his electric light bulbs, lighting of the house, a laboratory and a few adjacent streets. It was the first lamp with a long service life, suitable for mass production. But as the production of strands of bamboo appeared quite expensive, Edison developed a new way to manufacture them from specially treated cotton fibers. First, cotton was placed in a hot zinc-chloride solution, where it is gradually dissolved. The resulting liquid was concentrated by a pump to a dough and extruded through a thin tube into a vessel with an alcohol. Here it turned into a fine yarn and wound on the drum. The resulting thread by several intermediate operations freed from chlorine-zinc solution, dried, cut, embedded in v-shaped form and charred in an oven without air. Then thread a thin sprayed layer of coal. For this, they were placed in a hood filled illuminating gas, and current is passed through them. Under the influence of the current gas decomposed and deposited on the thread a thin layer of carbon. After all these complex operations thread was ready for use.

light bulb manufacturing process was also very difficult. The thread is placed in a glass cap between the two platinum electrodes, fusing into the glass (pricey platinum had to use because it was identical to the glass coefficient of thermal expansion, which was very important to create a seal). Finally, with a mercury bulb pump of pumped air, so that it was no more than one-billionth of air which is contained therein at atmospheric pressure. When pumping over, the bulb sealed and is placed on the base with contacts for screw-in cartridge (and the cartridge and base, as well as many other elements of the electric lighting, remained unchanged to the present day - switches, fuses, electric meters and more - were also Edison invented). The average longevity of Edison's light bulb was 800-1000 hours of continuous burning.

Almost thirty years of light bulbs manufactured in the manner described above, but the future was for the lights with metallic thread. Even in 1890 Lodygin invented to replace coal thread metal wire of refractory tungsten filament which had 3385 degrees temperature. However, industrial production of light bulbs started only in the XX century.

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