For example, a tungsten filament designed to operate at 2727☌ (with a resistivity of 90,4 x 10-6 ) decreases its resistivity down to its mere 6% ( 5,65 x 10-6 )at a room temperature. Rush current, Resistance of filament changes dramatically by its working temperature. Luminous flux refers visible light using clear quartz glass tube. Characteristics, Some important characteristics can be estimated with the equation illustrated in the appendix 4. Light produced with a higher temperature filament has more bluish spectrum, which gives an impression of whiter light to human eyes. Higher filament temperature will increase the ratio of visible light, which belongs to rather short wavelength band of emission from a halogen lamp. This results in building up higher gas pressure inside, suppressing tungsten vaporization, thus achieving long life as well as better lumen maintenance performance as shown in the appendix 2. In order to achieve good halogen cycle, halogen lamps have generally much compact bodies (made of quartz to withstand the high temperature) compared with conventional lamps. The free tungsten atom W can deposit itself onto a cold portion of the filament, but the X remains floated in the gas, repeating the process over and over. Since the temperature near the filament exceeds 2000☌, WX2 is disintegrated to W and Xs again. If the temperature at the quartz glass is above 250 ☌, which is over the condensati on temperature of WX2, the molecules can not condensate themselves on the wall, therefore circulate back towards the filament. Tungsten atoms W which have evaporated from the filament combine with halogen vapor to form WX2, which traverse towards the quartz glass wall. Halogen cycle, The appendix 1 illustrates chemical reaction inside a halogen lamp. Halogen lamps do not have this slow deterioration thanks to a chemical process that is called “halogen cycle”. Conventional incandescent lamps lose their light fluxgradually during the operation, due to tungsten vapor accumulation on inner bulb surfaces (blackening phenomenon). Its gas consists of not only inert gas which is commonly use in gas-filled lamp technology, but also small trace of halogen material. Because the temperature required for this reaction is higher than a typical incandescent bulb, halogen lamps must generally be manufactured using quartz.A halogen lamp is a kind of gas-fillet tungsten filament lamp. Some tungsten is returned to the filament, which also serves to increase the rated life of the lamp. Halogen lamps are largely able to eliminate this problem because the halogen gas reacts chemically with the evaporated tungsten to prevent it from affixing to the glass. This causes blackening of the lamp, which decreases light output and reduces life. In a typical incandescent lamp, tungsten slowly evaporates from the burning filament. How do they work?Ī halogen lamp functions identically to an incandescent lamp, with one notable exception: The halogen cycle. In 1959, General Electric patented a commercially viable halogen lamp using iodine as the halogen gas. The usage of chlorine to prevent blackening of the lamp was patented in 1882. The early history of the halogen lamp parallels that of the incandescent. They are known for moderately high efficiency, quality of light, and high rated life compared to regular incandescent lamps. The halogen light bulb or lamp is a type of incandescent lamp which uses a halogen gas in order to increase both light output and rated life.
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