Electric light

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Incandescent (left) and compact fluorescent (right) light bulbs turned on Lampadas.jpg
Incandescent (left) and compact fluorescent (right) light bulbs turned on

An electric light is a device that produces visible light from electric power. It is the most common form of artificial lighting and is essential to modern society, [1] providing interior lighting for buildings and exterior light for evening and nighttime activities. In technical usage, a replaceable component that produces light from electricity is called a lamp. [2] Lamps are commonly called light bulbs; for example, the incandescent light bulb. [3] Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the socket of a light fixture. The electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap.

Contents

The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, such as fluorescent lamps, and LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor.

Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, and fires. [4] English chemist Humphry Davy developed the first incandescent light in 1802, followed by the first practical electric arc light in 1806. By the 1870s, Davy's arc lamp had been successfully commercialized, and was used to light many public spaces. [5] Efforts by Joseph Swan and Thomas Edison led to commercial incandescent light bulbs becoming widely available in the 1880s, and by the early twentieth century these had completely replaced arc lamps. [1] [4]

The energy efficiency of electric lighting has increased radically since the first demonstration of arc lamps and the incandescent light bulb of the 19th century. Modern electric light sources come in a profusion of types and sizes adapted to many applications. Most modern electric lighting is powered by centrally generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems. Battery-powered light is often reserved for when and where stationary lights fail, often in the form of flashlights or electric lanterns, as well as in vehicles.

Elaborate light in Denver, Colorado Light in linger.jpg
Elaborate light in Denver, Colorado

Types

Electric light longevity and brightness testing in an integrating sphere Consumer Reports - product testing - electric light longevity and brightness testing.tif
Electric light longevity and brightness testing in an integrating sphere

Types of electric lighting include:

Different types of lights have vastly differing efficacies and color of light. [6]

Name Optical spectrum Nominal efficacy
(lm/W)
Lifetime (MTTF)
(hours)
Color temperature
(kelvin)
Color Color
rendering
index
Incandescent light bulb Continuous 4–172–2,5002,400–3,400Warm white (yellowish)100
Halogen lamp Continuous16–233,000–6,0003,200Warm white (yellowish)100
Fluorescent lamp Mercury line + Phosphor 52–100 (white)8,000–20,0002,700–5,000*White (various color temperatures), as well as saturated colors available15–85
Metal-halide lamp Quasi-continuous50–1156,000–20,0003,000–6,500White (various color temperatures), as well as saturated colors available65–93
Sulfur lamp Continuous80–11015,000–20,0006,000Pale green79
High pressure sodium Broadband55–14010,000–40,0001,800–2,200*Pinkish orange0–70
Low pressure sodium Narrow line100–20018,000–20,0001,800*Yellow, no color rendering0
LED lamp Line plus phosphor10–100 (white)50,000–100,000Various white from 2,700 to 6,000*Various color temperatures, as well as saturated colors70–85 (white)
Electrodeless lamp Mercury line + Phosphor 70–90 (white)80,000–100,000Various white from 2,700 to 6,000*Various color temperatures70–85 (white)

*Color temperature is defined as the temperature of a black body emitting a similar spectrum; these spectra are quite different from those of black bodies.

The most efficient source of electric light is the low-pressure sodium lamp. It produces, for all practical purposes, a monochromatic orange-yellow light, which gives a similarly monochromatic perception of any illuminated scene. For this reason, it is generally reserved for outdoor public lighting applications. Low-pressure sodium lights are favoured for public lighting by astronomers, since the light pollution that they generate can be easily filtered, contrary to broadband or continuous spectra.

Incandescent light bulb

Sign with instructions on the use of light bulbs This room is equipped with Edison electric light.jpg
Sign with instructions on the use of light bulbs
A tablet at St John the Baptist Church, Hagley commemorates the installation of electric light in 1934. Hagley, St John the Baptist - interior, Mason memorial.jpg
A tablet at St John the Baptist Church, Hagley commemorates the installation of electric light in 1934.

The modern incandescent light bulb, with a coiled filament of tungsten, and commercialized in the 1920s, developed from the carbon filament lamp introduced about 1880.

Less than 3% of the input energy is converted into usable light. Nearly all of the input energy ends up as heat that, in warm climates, must then be removed from the building by ventilation or air conditioning, often resulting in more energy consumption. In colder climates where heating and lighting is required during the cold and dark winter months, the heat byproduct has some value. Incandescent bulbs are being phased out in many countries due to their low energy efficiency.

As well as bulbs for normal illumination, there is a very wide range, including low voltage, low-power types often used as components in equipment, but now largely displaced by LEDs.

Halogen lamp

Halogen lamps are usually much smaller than standard incandescent lamps, because for successful operation a bulb temperature over 200 °C is generally necessary. For this reason, most have a bulb of fused silica (quartz) or aluminosilicate glass. This is often sealed inside an additional layer of glass. The outer glass is a safety precaution, to reduce ultraviolet emission and to contain hot glass shards should the inner envelope explode during operation. Oily residue from fingerprints may cause a hot quartz envelope to shatter due to excessive heat buildup at the contamination site. The risk of burns or fire is also greater with bare bulbs, leading to their prohibition in some places, unless enclosed by the luminaire.

Those designed for 12- or 24-volt operation have compact filaments, useful for good optical control. Also, they have higher efficacies (lumens per watt) and better lives than non-halogen types. The light output remains almost constant throughout their life.

Fluorescent lamp

Top, two compact fluorescent lamps. Bottom, two fluorescent tube lamps. A matchstick, left, is shown for scale. Leuchtstofflampen-chtaube050409.jpg
Top, two compact fluorescent lamps. Bottom, two fluorescent tube lamps. A matchstick, left, is shown for scale.

Fluorescent lamps consist of a glass tube that contains mercury vapour or argon under low pressure. Electricity flowing through the tube causes the gases to give off ultraviolet energy. The inside of the tubes are coated with phosphors that give off visible light when struck by ultraviolet photons. [7] They have much higher efficiency than incandescent lamps. For the same amount of light generated, they typically use around one-quarter to one-third the power of an incandescent. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Fluorescent lamp fixtures are more costly than incandescent lamps, because they require a ballast to regulate the current through the lamp, but the lower energy cost typically offsets the higher initial cost. Compact fluorescent lamps are available in the same popular sizes as incandescent lamps and are used as an energy-saving alternative in homes. Because they contain mercury, many fluorescent lamps are classified as hazardous waste. The United States Environmental Protection Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal, and some jurisdictions require recycling of them. [8]

LED lamp

LED lamp with E27 Edison screw base Led-lampa.jpg
LED lamp with E27 Edison screw base

The solid-state light-emitting diode (LED) has been popular as an indicator light in consumer electronics and professional audio gear since the 1970s. In the 2000s, efficacy and output have risen to the point where LEDs are now being used in lighting applications such as car headlights and brake lights, in flashlights and bicycle lights, as well as in decorative applications, such as holiday lighting. Indicator LEDs are known for their extremely long life, up to 100,000 hours, but lighting LEDs are operated much less conservatively, and consequently have shorter lives. LED technology is useful for lighting designers, because of its low power consumption, low heat generation, instantaneous on/off control, and in the case of single color LEDs, continuity of color throughout the life of the diode and relatively low cost of manufacture. LED lifetime depends strongly on the temperature of the diode. Operating an LED lamp in conditions that increase the internal temperature can greatly shorten the lamp's life.

Carbon arc lamp

The 15 kW xenon short-arc lamp used in the IMAX projection system. Xenon short arc 1.jpg
The 15 kW xenon short-arc lamp used in the IMAX projection system.
A mercury arc lamp from a fluorescence microscope. Microscope MercuryArcBulb Detail.jpg
A mercury arc lamp from a fluorescence microscope.

Carbon arc lamps consist of two carbon rod electrodes in open air, supplied by a current-limiting ballast. The electric arc is struck by touching the rod tips then separating them. The ensuing arc produces a white-hot plasma between the rod tips. These lamps have higher efficacy than filament lamps, but the carbon rods are short-lived and require constant adjustment in use, as the intense heat of the arc erodes them. The lamps produce significant ultraviolet output, they require ventilation when used indoors, and due to their intensity they need protection from direct sight.

Invented by Humphry Davy around 1805, the carbon arc was the first practical electric light. It was used commercially beginning in the 1870s for large building and street lighting until it was superseded in the early 20th century by the incandescent light. Carbon arc lamps operate at high power and produce high intensity white light. They also are a point source of light. They remained in use in limited applications that required these properties, such as movie projectors, stage lighting, and searchlights, until after World War II.

Discharge lamp

A discharge lamp has a glass or silica envelope containing two metal electrodes separated by a gas. Gases used include, neon, argon, xenon, sodium, metal halide, and mercury. The core operating principle is much the same as the carbon arc lamp, but the term "arc lamp" normally refers to carbon arc lamps, with more modern types of gas discharge lamp normally called discharge lamps. With some discharge lamps, very high voltage is used to strike the arc. This requires an electrical circuit called an igniter, which is part of the electrical ballast circuitry. After the arc is struck, the internal resistance of the lamp drops to a low level, and the ballast limits the current to the operating current. Without a ballast, excess current would flow, causing rapid destruction of the lamp.

Some lamp types contain a small amount of neon, which permits striking at normal running voltage with no external ignition circuitry. Low-pressure sodium lamps operate this way. The simplest ballasts are just an inductor, and are chosen where cost is the deciding factor, such as street lighting. More advanced electronic ballasts may be designed to maintain constant light output over the life of the lamp, may drive the lamp with a square wave to maintain completely flicker-free output, and shut down in the event of certain faults.

Form factors

Many lamp units, or light bulbs, are specified in standardized shape codes and socket names. Incandescent bulbs and their retrofit replacements are often specified as "A19/A60 E26/E27", a common size for these kind of light bulbs. In this example, the "A" parameters describe the bulb size and shape while the "E" parameters describe the Edison screw base size and thread characteristics.

Lamp life expectancy

Life expectancy for many types of lamp is defined as the number of hours of operation at which 50% of them fail, that is the median life of the lamps. Production tolerances as low as 1% can create a variance of 25% in lamp life, so in general some lamps will fail well before the rated life expectancy, and some will last much longer. For LEDs, lamp life is defined as the operation time at which 50% of lamps have experienced a 70% decrease in light output.

Some types of lamp are also sensitive to switching cycles. Rooms with frequent switching, such as bathrooms, can expect much shorter lamp life than what is printed on the box. Compact fluorescent lamps are particularly sensitive to switching cycles.

Public lighting

The total amount of artificial light (especially from street light) is sufficient for cities to be easily visible at night from the air, and from space. This light is the source of light pollution that burdens astronomers and others.

In this composite image from October 2012, human-made lights highlight particularly developed or populated areas of the Earth's surface, including the seaboards of Europe, the eastern United States, India, Japan and South Korea. City Lights 2012 - Flat map crop.jpg
In this composite image from October 2012, human-made lights highlight particularly developed or populated areas of the Earth's surface, including the seaboards of Europe, the eastern United States, India, Japan and South Korea.

Uses other than illumination

A clear glass 60 W light bulb Gluehlampe 01 KMJ.jpg
A clear glass 60 W light bulb

Electric lamps can be used as heat sources, for example in incubators, as infrared lamps in fast food restaurants and toys such as the Kenner Easy-Bake Oven.

Due to their nonlinear resistance characteristics, tungsten filament lamps have long been used as fast-acting thermistors in electronic circuits. Popular uses have included:

A stylized depiction of a light bulb features as the logo of the Turkish AK Party. [9] [10]

Circuit symbols

In circuit diagrams, lamps have two main types of symbols, indicating their respective functions. These are:

Cultural symbolism

In Western culture, a lightbulb — in particular, the appearance of an illuminated lightbulb above a person's head — signifies sudden inspiration.

See also

Related Research Articles

Incandescent light bulb Electric light with a wire filament heated until it glows

An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidation. Current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections.

Halogen lamp Incandescent lamp variety

A halogen lamp is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a small amount of a halogen, such as iodine or bromine. The combination of the halogen gas and the tungsten filament produces a halogen-cycle chemical reaction, which redeposits evaporated tungsten on the filament, increasing its life and maintaining the clarity of the envelope. This allows the filament to operate at a higher temperature than a standard incandescent lamp of similar power and operating life; this also produces light with higher luminous efficacy and color temperature. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination. The small glass envelope may be enclosed in a much larger outer glass bulb, which has a lower temperature, protects the inner bulb from contamination, and makes the bulb mechanically more similar to a conventional lamp.

Timeline of lighting technology

Artificial lighting technology began to be developed tens of thousands of years ago and continues to be refined in the present day.

Arc lamp Light created by electrical breakdown of gas

An arc lamp or arc light is a lamp that produces light by an electric arc.

Fluorescent lamp Light source

A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. For comparison, the luminous efficacy of an incandescent bulb may only be 16 lumens per watt.

Flashlight Portable hand-held electric light

A flashlight or torch is a portable hand-held electric lamp. Formerly, the light source typically was a miniature incandescent light bulb, but these have been displaced by light-emitting diodes (LEDs) since the mid-2000s. A typical flashlight consists of the light source mounted in a reflector, a transparent cover to protect the light source and reflector, a battery, and a switch, all enclosed in a case.

Gas-filled tube Assembly of electrodes at either end of an insulated tube filled with gas

A gas-filled tube, also commonly known as a discharge tube or formerly as a Plücker tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Gas-filled tubes exploit phenomena related to electric discharge in gases, and operate by ionizing the gas with an applied voltage sufficient to cause electrical conduction by the underlying phenomena of the Townsend discharge. A gas-discharge lamp is an electric light using a gas-filled tube; these include fluorescent lamps, metal-halide lamps, sodium-vapor lamps, and neon lights. Specialized gas-filled tubes such as krytrons, thyratrons, and ignitrons are used as switching devices in electric devices.

Sodium-vapor lamp Type of electric lamp

A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm.

High-intensity discharge lamp Type of electric lamp/bulb

High-intensity discharge lamps are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with noble gas and often also contains suitable metal or metal salts. The noble gas enables the arc's initial strike. Once the arc is started, it heats and evaporates the metallic admixture. Its presence in the arc plasma greatly increases the intensity of visible light produced by the arc for a given power input, as the metals have many emission spectral lines in the visible part of the spectrum. High-intensity discharge lamps are a type of arc lamp.

Mercury-vapor lamp Electric lighting source

A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from the ultraviolet radiation the light produces, and a convenient mounting for the fused quartz arc tube.

Compact fluorescent lamp Fluorescent lamps with folded tubes, often with built-in ballast

A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube that is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.

Street lighting in the United States was introduced by inventor Benjamin Franklin, who was the postmaster of Philadelphia, Pennsylvania. For this reason, many regard Philadelphia as the birthplace of street lighting in the US.

Metal-halide lamp Type of lamp

A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides. It is a type of high-intensity discharge (HID) gas discharge lamp. Developed in the 1960s, they are similar to mercury vapor lamps, but contain additional metal halide compounds in the quartz arc tube, which improve the efficiency and color rendition of the light. The most common metal halide compound used is sodium iodide. Once the arc tube reaches its running temperature, the sodium dissociates from the iodine, adding orange and reds to the lamp's spectrum from the sodium D line as the metal ionizes. As a result, metal-halide lamps have high luminous efficacy of around 75–100 lumens per watt, which is about twice that of mercury vapor lights and 3 to 5 times that of incandescent lights and produce an intense white light. Lamp life is 6,000 to 15,000 hours. As one of the most efficient sources of high CRI white light, metal halides as of 2005 were the fastest growing segment of the lighting industry. They are used for wide area overhead lighting of commercial, industrial, and public places, such as parking lots, sports arenas, factories, and retail stores, as well as residential security lighting, automotive headlamps and indoor cannabis grow operations.

Electrodeless lamp

The internal electrodeless lamp, induction lamp, or electrodeless induction lamp is a gas-discharge lamp in which an electric or magnetic field transfers the power required to generate light from outside the lamp envelope to the gas inside. This is in contrast to a typical gas discharge lamp that uses internal electrodes connected to the power supply by conductors that pass through the lamp envelope. Eliminating the internal electrodes provides two advantages:

Hydrargyrum medium-arc iodide lamp

Hydrargyrum medium-arc iodide (HMI) is the trademark name of Osram's brand of metal-halide gas discharge medium arc-length lamp, made specifically for film and entertainment applications. Hydrargyrum comes from the Greek name for the element mercury.

Gas-discharge lamp Artificial light sources powered by ionized gas electric discharge

Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionized gas, a plasma.

Light fixture Electrical device with an electric lamp

A light fixture, light fitting, or luminaire is an electrical device containing an electric lamp that provides illumination. All light fixtures have a fixture body and one or more lamps. The lamps may be in sockets for easy replacement—or, in the case of some LED fixtures, hard-wired in place.

Stage lighting instrument

Stage lighting instruments are used in stage lighting to illuminate theatrical productions, concerts, and other performances taking place in live performance venues. They are also used to light television studios and sound stages.

LED lamp Light source

An LED lamp or LED light bulb is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and can be significantly more efficient than most fluorescent lamps. The most efficient commercially available LED lamps have efficiencies of 200 lumen per watt (Lm/W). Commercial LED lamps have a lifespan many times longer than incandescent lamps.

United States Lighting Energy Policy is moving towards increased efficiency in order to lower greenhouse gas emissions and energy use. Lighting efficiency improvements in the United States can be seen through different standards and acts. The Energy Independence and Security Act of 2007 laid out changes in lighting legislation for the United States. This set up performance standards and the phase-out of incandescent light bulbs in order to require the use of more efficient fluorescent lighting. EISA 2007 is an effort to increase lighting efficiency by 25-30%. Opposition to EISA 2007 is demonstrated by the Better Use of Light Bulbs Act and the Light Bulb Freedom of Choice Act. The efforts to increase lighting efficiency are also demonstrated by the Energy Star program and the increase efficiency goals by 2011 and 2013.

References

  1. 1 2 Reisert, Sarah (2015). "Let There be Light". Distillations Magazine. 1 (3): 44–45. Retrieved 22 March 2018.
  2. "Lamp". Dictionary.com. Retrieved November 9, 2014.
  3. "Light bulb". Merriam-Webster. Retrieved September 18, 2017.
  4. 1 2 Freebert, Ernest (2014). The Age of Edison: Electric Light and the Invention of Modern America. Penguin Books. ISBN   978-0-14-312444-3.
  5. Guarnieri, M. (2015). "Switching the Light: From Chemical to Electrical" (PDF). IEEE Industrial Electronics Magazine. 9 (3): 44–47. doi:10.1109/MIE.2015.2454038. hdl: 11577/3164116 . S2CID   2986686.
  6. Brown, Martin T. (2003) Memorandum from Martin T Brown. UK Parliament
  7. Perkowitz, Sidney; Henry, A. Joseph (23 November 1998). Empire of Light:: A History of Discovery in Science and Art. Joseph Henry Press. ISBN   978-0-309-06556-6.
  8. United States Environmental Protection Agency, OSWER (2015-07-23). "Hazardous Waste". US EPA. Retrieved 3 November 2018.
  9. Thomson Reuters (2013-06-29). "A protester holds a light bulb, the official symbol of Turkey's ruling AK Party (AKP), with a Nazi swastika sign painted on it during an anti-government protest at Taksim Square in Istanbul". news.trust.org. Retrieved 2018-11-03.
  10. Kutlugun, Satuk Bugra and Akcay, Ahmet Sait (14 August 2016). "15 years of Turkey's Justice and Development Party". Anadolu Agency.{{cite web}}: CS1 maint: multiple names: authors list (link)