The earliest form of light bulbs contained carbon filaments. These were in use until the turn of the century, when the tungsten filament was invented. Incandescent bulbs today still use tungsten filaments.
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Contrary to popular belief, the electric light was invented in 1809 by a chemist named Humphry Davy. He was able to create an arc of light by connecting a carbon strip to the ends of two wires which were connected to a battery. The main drawback was that the carbon filament did not burn very long. Electric light sources used variations of this method until 1876, when Thomas Edison created a carbon filament that would burn for 40 hours.
Thomas Edison did two things to bring the light bulb into popular use: Not only did he invent a filament that would burn for 40 hours, he also placed the wires inside a vacuum bulb. This idea was based on a patent issued to Henry Woodward and Matthew Evans in 1875. Edison bought the patent from them in 1879.
The Move to Tungsten
In 1906, General Electric was issued a patent for a method to make tungsten filament light bulbs, though they were very expensive to produce. In 1910, William David Coolidge created a way to bring down the cost of the new lights, and they quickly replaced the old-style carbon filament bulbs.
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