Thermal radiation is due to a phenomenon caused by the internal thermal motion object. Any object thermal radiation phenomenon. The higher the temperature, the greater the thermal radiation intensity. At the time of low temperature radiates infrared light; When the temperature reaches 500 degrees Celsius produce red visible light; Incandescent light when 1500 degrees Celsius. Thermal radiation spectrum is a continuous spectrum. Made according to the principle of thermal radiation light source is called thermal radiation light source. Incandescent electric light source is made according to the principle of thermal radiation. It depends on the current heating filament and shine. Work in hot state and called in the filament incandescent lamp, ordinary incandescent filament is commonly spiral tungsten filament, housed in a transparent glass shell, can be a vacuum or inert gas filling. Incandescent lamp general under 40 w is true it light bulbs, more than 40 w for inflatable light bulb. Incandescent lamp is characterized by low price, simple line, does not need auxiliary device can be directly lit, can work under wide temperature, the approximate point light, convenient for good optical control. The deficiency is that relatively low luminous efficiency, 10 - 25 lm / W) ; Lighting glass shell temperature is higher; Life is short ( 1000h) ; Service life is greatly influenced by power supply voltage changes, voltage, an 5% increase in life expectancy nearly 20%; Infrared radiation is big, influence scope; Due to vibration or heated affected by mechanical vibration and shortens life. Incandescent bulbs are not vacuum. Usually 40 w incandescent lamp is under vacuum, over 40 w lamp is inflated. Is commonly nitrogen filled argon gas mixture, the nitrogen - 8% 14%, 86% argon - 92%. Although filling the krypton and xenon gas heat conduction loss is smaller, but because of the expensive only in special light bulbs. YanZhiXiang
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