A light bulb is a device consisting of a metal filament that emits light when heated to incandescence by electricity. An early form of light bulb dates to 1860, when Joseph Swan made a workable model. In 1879 Thomas Edison patented an improved design in the US.
Modern light bulbs comprise a filament enclosed by a glass envelope in a vacuum containing a noble gas such as argon. The filament is usually made of tungsten because of its high tensile strength, low evaporation, and high efficiency in converting electrical energy into light as it glows white hot.
Related category TECHNOLOGY
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