1850, the Englishman Joseph Wilson Swan began to study electric lights. 1878, he obtained a British patent for a light bulb powered by carbon wire under vacuum, and started to set up a company in Britain to install electric lights in every household.
1874, two Canadian electrical technicians applied for a patent for electric lamps. They filled helium gas under the glass bubble, and the charged carbon rod would glow. But they didn't have enough financial resources to continue developing this invention, so they sold the patent to Edison at 1875.
Edison tried to improve the filament after buying the patent. 1879, he changed to carbon filament to make a light bulb, which successfully lasted 13 hours. By 1880, his carbonized bamboo filament bulb had been successfully maintained in the laboratory for 1200 hours. But in Britain, Swan sued Edison for patent infringement and won. Edison's electric light company in England was forced to make Swan a partner. But later Swan sold his rights and patents to Edison. In America, Edison's patent has also been challenged. The United States Patent Office once ruled that his invention had a criminal record and was invalid. Finally, after years of litigation, Edison obtained the patent right of carbon filament incandescent lamp.
Edison's greatest discovery was that tungsten was used as the filament instead of carbon. Later, in 1906, General Electric invented the manufacturing method of tungsten wire for electric lamps. Finally, the method of manufacturing tungsten filament at a low price was solved, and the tungsten filament bulb has been used ever since.
The biggest problem of light bulb is the evaporation of filament. The temperature is different because of the tiny resistance difference on the tungsten wire. Where the resistance is high, the temperature rises higher and the tungsten filament evaporates faster, which leads to the tungsten filament becoming younger and the resistance further increasing. Finally, the tungsten wire burns out. Later, it was found that replacing vacuum with inert gas could slow down the evaporation of tungsten wire. Today, most light bulbs are filled with helium, argon or krypton.
The life of modern incandescent lamps is generally about 1 1,000 hours.
halogen lamp
Halogen bulb under ultraviolet filter
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Halogen bulb under ultraviolet filter
Halogen lamp, also known as tungsten halogen lamp, is a kind of incandescent lamp. The principle is to inject halogen gas such as iodine or bromine into the bulb. At high temperature, the evaporated tungsten wire reacts chemically with halogen, and the evaporated tungsten will solidify again on the tungsten wire to form a balanced cycle to avoid premature fracture of the tungsten wire. Therefore, halogen bulbs last longer than incandescent lamps. In addition, halogen bulbs can work at a higher temperature than ordinary incandescent lamps, with higher brightness and efficiency. However, at this temperature, ordinary glass may soften. Therefore, halogen bulbs need to use timely glass with higher melting point. Because timely glass can't block ultraviolet rays, halogen bulbs usually need to use additional ultraviolet filters.
If there is oil in the crystal glass on the halogen bulb, it will cause different temperatures on the glass and reduce the life of the bulb. Therefore, when replacing halogen bulbs, people should avoid touching the glass of the bulbs. If your finger touches it, wash it with alcohol.
efficacy
Most incandescent lamps will convert 90% of the consumed energy into useless heat energy, and less than 10% will become light. In contrast, fluorescent lamps (also known as tubes) are much more efficient, close to 40%, and produce only one-sixth of the heat of incandescent lamps with the same brightness. Therefore, in many places, especially shopping malls, buildings that need air conditioning in summer will use fluorescent lamps to save electricity. Small fluorescent lamps (energy-saving bulbs) combine fluorescent lamps with starting electronic equipment, and use the interface of standard bulbs to replace ordinary incandescent bulbs. For example, a 26-watt energy-saving light bulb emits 1 1W brightness and 15W heat. An incandescent bulb with the same brightness 1 1 watt consumes four times more power, reaching 100 watt; It releases more than six times the heat, reaching 90 watts.
Many household lamps are mainly ordinary incandescent lamps. Halogen bulbs have become more and more popular in recent years, especially when the light source needs to be concentrated, such as spotlights at home and headlights of cars. A good halogen bulb can achieve the efficiency of 15%. For example, a 60-watt halogen bulb has the same brightness as an ordinary bulb of 100 watt. However, halogen bulbs are small in size and work at high temperatures. When used at home, it needs special protection to prevent fire.