GREAT WALL OF CHINA History of the Great Wall of China: The Great Wall of China is the national military defense project in the cold weapon war era with the longest time and the largest amount of construction in the world. It condenses the sweat and wisdom of our ancestors and is the symbol and pride of the Chinese nation. According to historical records, since the Warring States period, more than 20 vassals and feudal dynasties have built the Great Wall. The earliest was the Chu Kingdom. To defend the nomadic or enemy countries in the north, they began to build the Great Wall. Subsequently, Qi, Yan, Wei, Zhao, Qin, and other countries also began to build their own Great Wall for the same purpose. After Qin unified the six countries, the famous emperor Qin Shihuang sent Meng Tian northward to the Xiongnu, connecting the Great Walls of various countries. From Linyao in the west to Liaodong in the east, it stretched for more than 10,...
WHO INVENTED THE LIGHT BULB?
Without her, our life would be much more uncomfortable. And there is no home, or car, or bicycle that doesn't use at least one. Let's discover the secrets of the incandescent light bulb and its ... modern granddaughters!
The incandescent light bulb is the classic invention that has several fathers. The first father was the British inventor Sir Joseph Wilson Swan who patented it in 1878. It was his home in Gateshead, Great Britain, the first house in the world to be illuminated with electric bulbs. Three years later, in 1881, the Savoy theater in the City of Westminster (London) was the first public building to use incandescent bulbs.
The bulb invented by Swan was made of a thick carbon filament which, when heated, emitted light and gas. This idea, however, had some flaws: the inside of the bulb quickly covered itself with soot emitted by the incandescent filament and thus blackened. Also, this type of bulb consumed a lot of electricity.
COPY INVENTORS
The American Thomas Edison thought to improve the bulb the following year (1879), who patented a bulb with a thin filament and high electrical resistance. Unlike Swan's model, Edison's bulb did not blacken the inside of the bulb too much and therefore maintained a constant brightness. Swan, starting with Edison's modifications, further improved the light bulb and began selling his own in England.
Thus, between the two inventors, a dispute arose over the authorship of the invention. The dispute ended years later with the creation of the Edison-Swan company which became one of the world's largest manufacturers of light bulbs. In 1910 the American physicist William David Coolidge replaced the carbon filament with one of tungsten immersed in a gas, thus creating a bulb that lasted much longer. This type of lamp, with very few variations, has come down to the present day.
WHY IS THE LIGHT BULB LIGHT?
When the tungsten filament of a light bulb is passed through by electric current, a certain number of electrons reaches an energy level higher than normal. When this energy transforms, because electrons return to their normal energy level, it creates luminous particles called photons, which is light.
Unfortunately, this process is very inefficient in fact, in an incandescent bulb, just 10 percent of the energy it receives turns into visible light. The remaining 90 percent become infrared light (which human eyes cannot see) and heat (which, on the other hand, we can feel: just bring a hand close to a lit lamp!).
CURIOUS BULBS
In 1879, the Turin inventor of Piossasco Alessandro Cruto managed to make a carbon filament for incandescent bulbs that lasted 500 hours compared to the 40 hours of the filament of Edison's bulbs. Unfortunately, having no financiers, he was unable to patent his invention and lost his memory.
THREE BRIGHT CURIOSITIES
For a tungsten filament to emit visible light, it must reach a very high temperature: about 2,200 degrees centigrade!
The filament of a normal bulb is incredibly long: about two meters. And it is so thin that, to fit everything inside a light bulb, it must be wrapped in the form of a double coil.
Modern bulbs are not vacuum-packed and contain no air but an inert gas. Inert gas is a type of gas that has no unwanted chemical reactions.
The inert gas (usually it is a gas called argon ), serves to prevent the tungsten filament, evaporating due to the very high temperature it reaches, quickly consumes by burning the bulb.
The European Union has gradually banned the sale of incandescent bulbs because they consume too much energy. Instead of normal bulbs,
halogen lamps (a variant of incandescent ones, with greater efficiency and longer life), low-consumption fluorescent lamps and LED lamps can be used. The latter two types of lamps, with the same emitted light, consume up to 80 percent less energy.
Comments
Post a Comment
Please do not enter any spam link in the comment box.