Incandescent light bulb
Electric light producing illumination by Joule heating a filament.
An incandescent light bulb—also called an incandescent lamp or globe—works by sending an electric current through a thin wire, or filament, which heats up so much that it glows and gives off light. This process is called Joule heating. The filament sits inside a glass bulb that has either had the air removed or been filled with an inert gas, which stops the filament from burning up. Wires embedded in the glass carry electricity to the filament, and a socket holds the bulb in place while connecting it to the power supply.
These bulbs come in many sizes, brightness levels, and voltages, ranging from 1.5 volts up to about 300 volts. They don’t need any extra equipment to regulate them, are cheap to make, and work just as well on alternating current as on direct current. Because of this, they were once everywhere: in homes and businesses, in portable lamps, car headlights, flashlights, and even in decorative and advertising lights.
But incandescent bulbs are far less efficient than other types of electric lighting. Less than 5% of the energy they use turns into visible light; the rest becomes heat. A typical 120-volt bulb gives off about 16 lumens per watt, and a 230-volt version gives about 13 lumens per watt. Compare that to a compact fluorescent bulb at 60 lumens per watt or a white LED at 100 lumens per watt. As a result, incandescent bulbs have lost a lot of market share to LEDs. This shift has been sped up by government bans meant to cut energy use, though some of those bans have sparked debate.
Historians Robert Friedel and Paul Israel have pointed out that many inventors worked on incandescent lamps before Joseph Swan and Thomas Edison. They argue that Edison’s version was the first truly practical one because he combined four things: a good incandescent material, a very high vacuum, a high-resistance filament that made it economical to distribute power from a central source, and the development of all the other parts needed for a large-scale lighting system. Joseph Swan’s bulb was demonstrated in 1878 and installed for daily use in London in 1881, while Edison’s first public demonstration came in 1879—meaning their work was roughly contemporaneous, with neither clearly predating the other.
- inventors
- Historians Robert Friedel and Paul Israel list inventors prior to Joseph Swan and Thomas Edison; Edison's version was the first practical implementation due to an effective incandescent material, a hi
- first_practical_implementation
- Thomas Edison (Edison Electric Light Company)
- predecessor
- Joseph Swan's incandescent light bulb was demonstrated in 1878 and installed for daily use in London in 1881, roughly contemporaneous with Edison's 1879 demonstration.
- field
- Electric lighting
- known_for
- Providing illumination via Joule heating of a filament; basis for household and commercial lighting for over a century.
Lore & Background
Early research into incandescent lighting began in 1761 when Ebenezer Kinnersley demonstrated heating a wire to incandescence, though such wires tended to melt or oxidize rapidly in air. In 1802, Humphry Davy used a large battery to create an incandescent light by passing current through a thin strip of platinum, chosen for its high melting point; it was not bright enough or long-lasting to be practical, but it inspired scores of experimenters over the next 75 years. In 1838, Marcellin Jobard invented an incandescent light bulb using a carbon filament in a vacuum.
Reader's Guide
The incandescent light bulb was a transformative technology that enabled widespread electric lighting in homes, businesses, and public spaces. Its significance lies in its simplicity and low manufacturing cost, requiring no external regulating equipment and working on both alternating and direct current. However, its low efficiency—converting less than 5% of energy into visible light—led to its decline in market share compared to more efficient technologies like compact fluorescent and LED lamps. Government bans aimed at reducing energy consumption have accelerated this decline, though such bans have been controversial. Historians Robert Friedel and Paul Israel note that Thomas Edison's version was the first practical implementation due to a combination of an effective incandescent material, a high vacuum, high resistance for economic power distribution, and development of a complete lighting system. Joseph Swan's bulb pre-dated Edison's and was in daily use in London in 1881. Historian Thomas Hughes attributed Edison's business success to his development of an entire, integrated system of electric lighting, of which the lamp was a small component. Other inventors with comparable ingenuity have been forgotten because they did not introduce their inventions within such a system.
Did You Know?
- Less than 5% of the energy consumed by an incandescent bulb is converted into visible light; the rest is released as heat.
- Joseph Swan's incandescent light bulb pre-dated Thomas Edison's and was installed and in daily use in London in 1881.
- The government of Canada maintains that Henry Woodward and Mathew Evans invented the lightbulb, filing a patent in 1874.
- Incandescent bulbs work equally well on either alternating current or direct current.
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