An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. Upper left: fluorescent lamp, upper right: incandescent bulb, lower left: white LED, lower right: candle flame. The efficiency of the lamp increases with a larger filament diameter. The socket provides electrical connections and mechanical support, and allows changing the lamp when it burns out. Higher molecular weight gasses have lower thermal conductivity, because both the molecular weight is higher and also the cross sectional area is higher. Filament temperatures depend on the filament type, shape, size, and amount of current drawn. He devised a method of treating cotton to produce 'parchmentised thread' in the early 1880s and obtained British Patent 4933 that same year. How it works, History, Inventors and Examples. By definition, the maximum efficacy is 683 lm/W for monochromatic green light. Filing year 1874: Electric Light", "Henry Woodward and Mathew Evans Lamp retrieved 2010 February 16", https://ilglobo.com/news/alessandro-crutos-incandescent-light-bulb-33135/, "Switching the Light: From Chemical to Electrical", "Dec. 18, 1878: Let There Be Light — Electric Light", "Sir Joseph William Swan FRS (RSC National Chemical Landmark)", "Thomas Edison: Original Letters and Primary Sources", "The Nernst Lamp. A hot glass bulb may fracture on contact with cold objects. [61] Early bulbs had a life of up to 2500 hours, but in 1924 a cartel agreed to limit life to 1000 hours. Metallized or "graphitized" filaments were first heated to high temperature to transform them into graphite, which further strengthened and smoothed the filament. From 1898 to around 1905, osmium was also used as a lamp filament in Europe. Very low voltages are inefficient since the lead wires would conduct too much heat away from the filament, so the practical lower limit for incandescent lamps is 1.5 volts. In the past, we bought lightbulbs based on how much energy, or watts, they use. And when there are no more particles to burn, the light bulb burns out, which typically takes place 800-1,200 hours into the life of the incandescent light bulb. These can be both living and non living things. These arc lamps ran on relatively low voltages and incorporated tungsten filaments to start ionization within the envelope. Since tantalum metal has a lower resistivity than carbon, the tantalum lamp filament was quite long and required multiple internal supports. Consol. Very small lamps may have the filament support wires extended through the base of the lamp for connections. When tungsten filaments were introduced, about 50 million lamp sockets existed in the US. Together, the filling and coating recycle heat to keep the filament hot with less electricity. An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. Light bulbs using coiled coil filaments are sometimes referred to as 'double-coil bulbs'. [62] The equivalent of a drop of water distributed over 500,000 lamps will significantly increase darkening. Incandescent light is emitted from a heated object. [49], In 1896 Italian inventor Arturo Malignani (1865–1939) patented an evacuation method for mass production, which allowed obtaining economic bulbs lasting 800 hours. More than 95% of the power consumed by a typical incandescent light bulb is converted into heat rather than visible light. An upper limit for incandescent lamp luminous efficacy is around 52 lumens per watt, the theoretical value emitted by tungsten at its melting point. If a light bulb envelope leaks, the hot tungsten filament reacts with air, yielding an aerosol of brown tungsten nitride, brown tungsten dioxide, violet-blue tungsten pentoxide, and yellow tungsten trioxide that then deposits on the nearby surfaces or the bulb interior. 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