Light bulb

From Conservapedia - Reading time: 4 min

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The electric light bulb is a device which converts electricity into light. A typical "light bulb" is an incandescent light source which operates in an oxygen-depleted environment (either a vacuum, or a space filled with an inert gas such as nitrogen or argon). However, incandescence also emits great deal of heat, and a wide spectrum of electromagnetic radiation, only some of which is in the visible spectrum. Therefore, newer alternatives have come about in an attempt to reduce this wasted energy. These replacement devices are also typically referred to as "light bulbs."

Incandescent[edit]

An incandescent bulb produces light when an electric current is run through a thin, resistive but somewhat conductive filament, causing it to rapidly become white hot. Unfortunately, this results in about 90 percent of the consumed electricity being converted into heat, rather than photons.^[1] Most materials including metals typically oxidize very quickly under these conditions, so this filament is placed in a vacuum, so that the filament cannot oxidize. This enables it to produce significant amounts of light, without promptly burning out. Modern light bulbs use Tungsten wire, because it has a very high melting temperature.

History[edit]

Although Humphry Davy was the first known inventor of an electric-powered light, his creation was simply an arc lamp which burned out very quickly.
Thomas Edison is traditionally known as the inventor of the incandescent light bulb. He experimented with materials and procedures, to produce a light bulb much like the kind we use today. However, he was not the first to invent a light bulb. There is a somewhat lengthy history behind the light bulb, as numerous people worked on the overall discovery. In 1840, the British scientist Warren de la Rue designed and created a light bulb using a coil of platinum wire. However, due to the high cost of platinum, this never became popular. Then in 1860, English chemist Joseph Swan produced a light bulb that used carbonized paper filaments. However, Swan's filaments did not last very long, and required a significant amount of current. In 1874, the Canadian inventors Henry Woodward and Matthew Evans also filed for a patent on their latest invention—an electric lamp which used carbon rods in a glass cylinder filled with nitrogen. Edison and his team, meanwhile, tested over 3,000 different designs for light bulbs between 1878 and 1880. In November 1879, Edison filed for a patent on an electric lamp which used a carbon filament, consisting of a variety of different materials, including cotton, linen and wood. Later, Edison switch to using carbonized bamboo filaments, which could burn for a longer period of time.^[2]

Nikola Tesla, a staunch competitor of Edison, also began working on light bulbs around this time time. This led to Tesla's invention of the fluorescent light, which was later put to use in CFL light "bulbs."^[3]

Later, William David Coolidge improved on General Electric's method of producing tungsten filaments, using modern machinery which was not available to the original inventors. This resulted in most incandescent light bulbs utilizing tungsten from then on.^[2]

Compact Fluorescent (CFL)[edit]

For a more detailed treatment, see Fluorescent lightbulb.

A fluorescent tube produces light by running high-voltage alternating current through a sealed glass tube, which contains an inert gas at low pressure, and a small amount of mercury. At each end of the tube, there are electrodes which create the pathway for a complete circuit. When electricity jumps from one electrode to the other across the mercury, light is produced. However, this light produced from the mercury is mostly ultraviolet, which is not visible to the human eye. To shift it into the visible light spectrum, the interior surface of the glass tube is generally coated with phosphor powder. This causes the tube to produce a rapidly pulsing visible light.^[4]

CFL "bulbs" use a small version of this. A thin glass tube is bent into a compact, curled shape, while maintaining a single entry and exit point at the base. Both electrodes are installed on the ends of the tube, in the base of the CFL "bulb." Most CFL bulbs have an integrated ballast (in the base of the bulb itself), which is the device responsible for getting the current moving through the tube. Some CFLs do not have an integrated ballast, meaning that they need a specialized base which contains this circuitry.^[5]

Light Emitting Diode (LED)[edit]

For a more detailed treatment, see Light emitting diode.

Unlike their predecessors, LED light bulbs do not need glass bulb to protect them from oxygen. LEDs themselves are very small, so there are generally one or more of them positioned in the base, with a hollow plastic "bulb" attached for them to shine into. This helps to disperse the light, and make it blend in with incandescent bulbs a little better. LEDs consume much less electricity than incandescent bulbs, and also less than CFLs. Additionally, LEDs do not typically burn out, since unlike incandescent and fluorescent bulbs, they do not have and kind of burning filament or electrode. However, their capability to output light slowly diminishes (a process formally known as lumen depreciation) as they are used. Therefore, their lifespan is generally considered to end when the light output has reduced by 30 percent.^[1]
Like CFLs, LEDs produce less heat than incandescent bulbs, but also like CFLs, that heat which is destructive the the internal electronics. The heat is absorbed by a heat sink in the bulb, which then attempts to release that heat into the air. However, if the bulb is used in an enclosure, this process is impaired, and the lamp will tend to degrade more quickly, or even fail completely.^[6][1]

References[edit]