Invention and Engineering

Incandescent light bulb

An incandescent light bulb, also known as an incandescent lamp or incandescent light globe, is an electric light that produces illumination by Joule heating a filament until it glows. The filament is enclosed in a glass bulb that is either evacuated or filled with inert gas to protect the filament from oxidation. Electric current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections. Incandescent bulbs are manufactured in a wide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment, have low manufacturing costs, and work equally well on either alternating current or direct current. As a result, the incandescent bulb became widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting. Incandescent bulbs are much less efficient than other types of electric lighting. Less than 5% of the energy they consume is converted into visible light; the rest is released as heat. The luminous efficacy of a typical incandescent bulb is 16 lumens per watt (lm/W) for a 120 V bulb or 13 lm/W for a 230 V bulb, compared with 60 lm/W for a compact fluorescent bulb or 100 lm/W for typical white LED lamps. As a result, incandescent bulbs have declined in market share compared to LED bulbs. This has been accelerated by government bans aimed at reducing energy consumption. These bans have been controversial in some cases.

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See also

• ▸Fraunhofer-Gesellschaft
• ▸Argyle diamond mine
• ▸19th-century London

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