Commercial Electric Light Bulb Invented - History

Commercial Electric Light Bulb Invented - History

Developing a commercial light bulb was the holy grail for inventors during much of the 19th century. Humphry Davy invented the first electric light in 1802. He produced a battery and then connected carbon to the battery making glow and thus creating light. His invention was called an arc light, but it had no commercial uses. in 1840, British scientist Warren de la Rue put a coiled platinum filament in a vacuum tube and passed an electric current through it. The design worked but the high cost of platinum made it an impractical invention. Canadian inventors Henry Woodward and Mathew Evans patented a light with a carbon filaments held between electrodes in glass filled with Nitrogen. They were not successful in commercializing the product.

In 1878 Thomas Edison began trying to invent a commercial viable light bulb. In October 1878 he filed his first patent for the “improvement of an electric light bulb. A year later he filed an additional patent to create a carbon filament using "cotton and linen thread, wood splints, papers coiled in various ways”. Soon after Edison and his assistance discovered that a carbonized bamboo filament would last 1,200 hours. This made a commercial light bulb feasible and began the era of electric light.

History of Electric Lamps and Lighting

History of electric lamps begins at about the same time when we used gas and kerosene to light houses and streets. It started humbly but it changed humanity from the foundations, from how we light things to much complex inventions.

First experiments in electrical illumination were made by Sir Humphry Davy, chemist and inventor, in the 19th century. He took a filament, made from platinum strip, and connected it to a battery, th biggest one in the world at the time and in 1802 made first prototype of an incandescent lamp. Electric current ran through platinum filament, heated it and filament started emitting light. Platinum was used as a material because of its high melting point. Lamp didn’t lasted long because heat burned the filament very quickly, but it was a starting point on which 20 and something inventors relied their ideas until we got first electric lamp that could be used for a longer time and with adequate strength of light. Prototype of a first electric arc lamp was made in 1809, again by Sir Humphry Davy and became basis for another type of electric lamp. In the years to come, many inventors experimented on the design of electric light. They changed materials of filament and tried different atmospheres inside a bulb - from better vacuum to noble gas. Sir Joseph Swann and Thomas Edison independently made first commercially usable electric light in 1870s. Main design idea, that prolonged working of the electric lamp, was using of carbon filament in better vacuum. That kind of electric lamp worked longer, up to 1200 hours, and gave better, stronger light. After that, filament was made from tungsten and used in the atmosphere of noble gas, which lessen evaporation of filament and gave longer lasting and even brighter light. At first, only few used electric lamps because of their high price but in time their use spread and it is estimated that by 1885, in the United States only, some 300.000 electric lamps were sold. Electric light spread across the world and is still here today as necessity. It has wide spectrum of uses in many parts of our lives from home to street lightning.

There are many variations of electric lamps but there are three general types:

- Incandescent lamps. Their main part is filament that conducts electric current that heats filament because of its resistance. Heated filament burns with bright light in an atmosphere of noble gas, enclosed in a glass bulb.

- Carbon arc lamps. These lamps are made like two electrodes that are connected to electric current and have slight distance between them. When the voltage is high enough, dielectric breakdown happens, gas in the bulb between the electrodes ionizes and bright spark appears.

- Gas discharge lamps. Lamps made in a tube shape with electrodes on the both ends and filled with gas that can conduct current when it is ionized, and emit light through its whole volume. Gas discharge lamps in the widest use are fluorescent and neon lamps.


The traditional flashbulb is another type of incandescent lightbulb. Early flash bulbs used a aluminum, zirconium, or magnesium filament or aluminum foil. Current was passed through the material and it glowed. The melting and boiling point of aluminum, magnesium or zirconium is so low that the lamp would vaporize the metal, which further intensified the brightness. Early lamps would last one flash and had to be replaced. Early flashbulbs often had an Edison type screw in thread like a regular lightbulb. Later lamps could last a few flashes. Later on disposable flash bulb arrays were developed to allow many flashes without switching bulbs.

One of the greatest challenges in developing a flash bulb is not the bulb itself, but timing the bulb to match the camera shutter. This improved with the development of solid state electronics in the 1950s.

Modern flashbulbs found on most cameras are no longer incandescent bulbs. They are tiny xenon arc tubes. An electric arc is formed through xenon gas. These have the great advantage of being reusable. They have the disadvantage of being a shorter duration than incandescent flash bulbs. This means they have to be more precisely time

1927 ?? at General Electric and Johannes Ostermeier both independently develop the first non-magnesium electric flashbulb. It is much safer than older bulbs. The General Electric Product is called the Sashalite. This light replaced dangerous magnesium powder lights. The new lamps burned aluminum foil in a bulb filled with oxygen. Ostermeier produced a product called the Vacublitz.
Schenectady, New York

1934 Philips Corp. Unknown inventor created the first modern flashbulb: it has a wire in an evacuated bulb. The wire burns ups in a more effective way than aluminum sheets of foil. This design has not changed much.

1960s ?? at Kodak develops the flashcube which has four single use small flash bulbs. The cube can be rotated to use the new bulb.

Rochester, New York

1968 John D. Harnden Jr. develops a both a static electronic photoflash assembly (1968) and disposable flashbulb lamp(1971) along with Bill Kornrumpf. The array of flash bulbs removes the need for replacing the bulb. This long plastic bar of bulbs was popular in the 1970s and 80s. Harnden also developed precise timing devices for the bulbs that used semiconductors which were new at the time.
Schenectady, New York

1968 William P. Kornrumpf developed the photoflash bulb assembly and disposable flashbulb array for low cost cameras along with John D. Harnden.
Schenectady, New York

World's First Light bulb Factory

Wait, we jump straight to Edison now? Not at all. Again, contrary to popular belief, the world's first ever light bulb manufacturing company was not made by Edison and was not built in the U.S.

Joseph Wilson Swan, another Englishman, almost perfected De la Rue's design in 1850. He used carbon paper filaments instead of platinum, enclosing it inside an evacuated glass vacuum. By 1860, he had a working prototype.

However the inadequate supply of electricity back then, and poor quality of vacuum manufacturing caused the short lifetime of the bulb. However, he didn't initially give up his pursuit for electric light.

By 1978, a year earlier than Edison's patent, he finally perfected his design with a longer-lasting bulb and eliminated the blackening issue with his cotton thread method.

He began installing light bulbs in houses and public venues, including his good friend, Sir William Armstrong's personal residence. His major breakthrough, however, came when he lit up London's famous theater The Savoy in 1881.

In the same year, he formed The Swan Electric Light Company Ltd at Benwell, Newcastle. By 1881, Swan is responsible for both the world's first light bulb commercial manufacturer and the world's first public building lit by electricity.

Who created the first vacuum light bulb?

In 1865, German chemist Herman Sprengel invented the Sprengel pump. It was vacuum technology they had all been waiting for. This advance in technology finally allowed scientists to place their light bulb filaments in vacuum chambers.

Sprengel mercury vacuum pump. A container of mercury (A) allowed by a valve (C) to fall one drop at a time into a long glass tube (XD) which empties into a reservoir (H). Air is trapped between the drops in the tube and carried by the weight of the mercury out the bottom of the tube. This slowly evacuates the container (R) attached at the top.

Commercial Electric Light Bulb Invented - History

February 13th, 2007 | Author: Administrator

1752 By tying a key onto a kite string during a storm, Ben Franklin , proved that static electricity and lightning were the same. His correct understanding of the nature of electricity paved the way for the future.

1800 First electric battery invented by Alessandro Volta. The “volt” is named in his honor.

1808 Humphry Davy invented the first effective “arc lamp.” The arc lamp was a piece of carbon that glowed when attached to a battery by wires.

1820 Separate experiments by Hans Christian Oersted, A.M. Ampere, and D.F.G. Arago confirmed the relationship between electricity and magnetism.

1821 The first electric motor was invented by Michael Faraday.

1826 Georg Ohm defined the relationship between power, voltage, current and resistance in “Ohms Law.”

1831 Using his invention the induction ring, Michael Faraday proved that electricity can be induced (made) by changes in an electromagnetic field. Faraday’s experiments about how electric current works, led to the understanding of electrical transformers and motors.
Joseph Henry separately discovered the principle of electromagnetic induction but didn’t publish his work. He also described an electric motor.

1832 Using Faraday’s principles, Hippolyte Pixii built the first “dynamo,” an electric generator capable of delivering power for industry. Pixxi’s dynamo used a crank to rotate a magnet around a a piece of iron wrapped with wire. Because this devise used a coil of wire, it produced spikes of electric current followed by no current.

1835 Joseph Henry invented the electrical relay, used to send electrical currents long distances.

1837 Thomas Davenport invented the electric motor, an invention that is used in most electrical appliances today.

1839 Sir William Robert Grove developed the first fuel cell, a device that produces electrical energy by combining hydrogen and oxygen.

1841 James Prescott Joule showed that energy is conserved in electrical circuits involving current flow, thermal heating, and chemical transformations. A unit of thermal energy, the Joule, was named after him.

1844 Samuel Morse invented the electric telegraph, a machine that could send messages long distances across wire.
1860’s Mathematical theory of electromagnetic fields published. J.C. Maxwell created a new era of physics when he unified magnetism, electricity and light. Maxwell’s four laws of electrodynamics (“Maxwell’s Equations”) eventually led to electric power, radios, and television.

1876 Charles Brush invented the “open coil” dynamo (or generator) that could produce a study current of electricity.

1878 Joseph Swan, and Englishman, invented the first incandescent lightbulb (also called an “electric lamp”). His lightbulb burned out quickly.
Charles Brush developed an arc lamp that could be powered by a generator.
Thomas Edison founded the Edison Electric Light Co. (US), in New York City. He bought a number of patents related to electric lighting and began experiments to develop a practical, long-lasting light bulb.

1879 After many experiments, Thomas Edison invented an incandescent light bulb that could be used for about 40 hours without burning out. By 1880 his bulbs could be used for 1200 hours.

1879 Electric lights (Brush arc lamps) were first used for public street lighting, in Cleveland, Ohio.
California Electric Light Company, Inc. in San Fransicso was the first electric company to sell electricity to customers. The company used two small Brush generators to power 21 Brush arc light lamps.

1881 The electric streetcar was invented by E.W. v. Siemens

1882 Thomas Edison opened th Pearl Street Power Station in New York City. The Pearl Street Station was one of the world’s first central electric power plants and could power 5,000 lights. The Pearl Street Station was a direct current (DC) power system, unlike the power systems that we use today which use alternating current (AC).
The first hydroelectric station opened in Wisconsin.
Edward Johnson first put electric lights on a Christmas tree.

1883 Nikola Tesla invented the “Tesla coil”, a transformer that changes electricity from low voltage to high voltage making it easier to transport over long distances. The transformer was an important part of Tesla’s alternating current (AC) system, still used to deliver electricity today.

1884 Nikola Tesla invented the electric alternator, an electric generator that produces alternating current (AC). Until this time electricity had been generated using direct current (DC) from batteries. AC electrical systems are better for sending electricity over long distances.
Steam turbine generator, capable of generating huge amounts of electricity, was invented by Sir Charles Algernon Parsons.

1886 William Stanley developed the induction coil transformer and an alternating current electric system.

1888 Nikola Tesla demonstrated the first “polyphase” alternating current (AC) electrical system. His AC system including everything needed for electricity production and use: generator, transformers, transmission system, motor (used in appliances) and lights. George Westinghouse, the head of Westinghouse Electric Company, bought the patent rights to the AC system.
The first use of a large windmill to generate electricity was built by inventor Charles Brush. He used the windmill to charge batteries in the cellar of his home in Cleveland, Ohio.

1893 The Westinghouse Electric Company used an alternating current (AC) system to light the Chicago World’s Fair.

A 22 mile AC powerline was opened, sending electricity from Folsom Powerhouse in California to Sacramento.

1896 An AC powerline that transmits power 20 miles from Niagra Falls to Buffalo, New York was opened.

1897 Electron discovered by Joseph John Thomson.

1900 Highest voltage transmission line 60 Kilovolt.

1901 First power line between USA and Canada at Niagra Falls.

1902 5-Megawatt turbine for Fisk St. Station (Chicago).

1903 First successful gas turbine (France).
World’s first all turbine station (Chicago).
Shawinigan Water & Power installs world’s largest generator (5,000 Watts) and world’s largest and highest voltage line—136 Km and 50 Kilovolts (to Montreal).

1908 Electric vacuum cleaner – J. Spangler.
Electric washing machine- A. Fisher.

1909 First pumped storage plant (Switzerland).

1911 Electric air conditioning – W. Carrier.

1913 T. Murray created the first air pollution control device, the “cinder catcher.”
Electric refrigerator – A. Goss.

1920 Federal Power Commission (FPC).

1921 Lakeside Power Plant in Wisconsin becomes the world’s first power plant to burn only pulverized coal.

1922 Connecticut Valley Power Exchange (CONVEX) starts, pioneering interconnection between utilities.

1923 Photoelectric cells were discovered.

1928 Construction of Boulder Dam begins.
Federal Trade Commission begins investigation of holding companies.

1933 Tennessee Valley Authority (TVA) established.

1935 Public Utility Holding Company Act.
Federal Power Act.
Securities and Exchange Commission.
Bonneville Power Administration.
First night baseball game in major leagues (Reds vs. Phillies) was played in Ohio on May 24th.

1936 Highest steam temperature reaches 900 degrees Fahrenheit vs. 600 degrees Fahrenheit in early 1920s.
Boulder (Hoover) Dam was completed. A 287 Kilovolt power line stretched 266 miles to Boulder (Hoover) Dam.
Rural Electrification Act.

1947 Transistor invented by scientists at Bell Telephone Laboratiories.

1953 First 345 Kilovolt transmission line.
First nuclear power station ordered in England.

1954 World’s first nuclear power plant (Russia) started generating electricity.
First high voltage direct current (HVDC) line (20 megawatts/1900 Kilovolts, 96 Km).
Atomic Energy Act of 1954 allows private ownership of nuclear reactors.

The history of the Light Bulb

The invention of the light bulb is sometimes attributed to Thomas Alva Edison, but today it is well-known that Heinrich Goebel built functional bulbs three decades earlier. Many others also contributed to the development of a practical device for the production of electrically generated lighting.

In 1801 Sir Humphry Davy, an English chemist, made platinum strips glow by passing an electric current through them, but the strips evaporated too quickly to make a useful lamp. In 1809 he created the first arc lamp, which he demonstrated to the Royal Institution of Great Britain in 1810, by creating a small but blinding arc between two charcoal rods connected to a battery.

In 1840 a British scientist Warren De la Rue enclosed a platinum coil in an evacuated tube and passed an electric current through it. The design was based on the concept that the high melting point of platinum would allow it to operate at high temperatures and that the evacuated chamber would contain less gas particles to react with the platinum, improving its longevity. Although it was an efficient design, the cost of the platinum made it impractical for commercial use.

In 1835 James Bowman Lindsay demonstrated a constant electric light at a public meeting in Dundee. He stated that he could “read a book at a distance of one and a half foot”. However having perfected the device, to his own satisfaction, he turned to the problem of wireless telegraphy and did not develop the electric light any further.

In 1841 Frederick de Moleyns of England was granted the first patent for an incandescent lamp, with a design using powdered charcoal heated between two platinum wires.

In 1854, the German inventor Heinrich Goebel developed the first ‘modern’ light bulb: a carbonized bamboo filament, in a vacuum bottle to prevent oxidation. In the following five years he developed what many call the first practical light bulb. His lamps lasted for up to 400 hours. He did not immediately apply for a patent, but his priority was established in 1893.

Joseph Wilson Swan(1828-1914) was a physicist and chemist born in Sunderland, England. In 1850 he began working with carbonized paper filaments in an evacuated glass bulb. By 1860 he was able to demonstrate a working device but lack of a good vacuum and an adequate supply of electricity resulted in a short lifetime for the bulb and inefficient light. By the mid-1870s better pumps became available, and Swan returned to his experiments. Swan received a British patent for his device in 1878. Swan reported success to the Newcastle Chemical Society and at a lecture in Newcastle in February 1879 he demonstrated a working lamp that utilized a carbon fibre filament. The most significant feature of Swan’s lamp was that there was little residual oxygen in the vacuum tube to ignite the filament, thus allowing the filament to glow almost white-hot without catching fire. From this year he began installing light bulbs in homes and landmarks in England and by the early 1880s had started his own company.

Across the Atlantic, parallel developments were also taking place. On July 24, 1874 a Canadian patent was filed for the Woodward and Evan’s Light by a Toronto medical electrician named Henry Woodward and a colleague Mathew Evans, who was described in the patent as a “Gentleman” but in reality a hotel keeper. They built their lamp with a shaped rod of carbon held between electrodes in an glass bulb filled with nitrogen. Woodward and Evans found it impossible to raise financial support for the development of their invention and in 1875 Woodward sold a share of their Canadian patent to Thomas Edison.

Edison purchased the Woodward and Evans patent and had a team of developers search for an alternative filament material. Eventually he used a carbon filament that burned for forty hours (first successful test was on October 21, 1879 it lasted 13 1/2 hours). Edison continued to improve their design. By 1880 he had a device that could last for over 1200 hours using a bamboo-derived filament, longer than the 400 hours of Heinrich Goebel’s earlier light bulb.

In January 1882, Lewis Latimer received a patent for the “Process of Manufacturing Carbons,” an improved method for the production of light-bulb filaments which yielded longer lasting bulbs than Edison’s technique.

In Britain, Swan took Edison to court for patent infringement. Edison lost and as part of the settlement, Edison was forced to take Swan in as a partner in his British electric works. The company was called the Edison and Swan United Electric Company. Eventually, Edison acquired all of Swan’s interest in the company. Swan sold his U.S. patent rights to the Brush Electric Company in June 1882.

Edison and his team did not find a commercially workable filament (bamboo) until more than 6 months after Edison filed the patent application. The weak and short lived (40-150 hours) carbon filament was eventually superseded by the tungsten filament. In 1903 Willis Whitnew invented a filament that would not make the inside of a lightbulb turn dark. It was a metal-coated carbon filament. In 1906, the General Electric Company were the first to patent a method of making tungsten filaments for use in incandescent lightbulbs. The filaments were costly, but by 1910 William David Coolidge (1873-1975) had invented an improved method of making tungsten filaments. The tungsten filament outlasted all other types of filaments and Coolidge made the costs practical


Types of electric lighting include:

    , a heated filament inside a glass envelope
      are incandescent lamps that use a fused quartz envelope filled with halogen gas
        , a fluorescent lamp designed to replace an incandescent lamp

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

      Name Optical spectrum Nominal efficacy
      Lifetime (MTTF)
      Color temperature
      Color Color
      Incandescent light bulb Continuous 4–17 2–20,000 2,400–3,400 Warm white (yellowish) 100
      Halogen lamp Continuous 16–23 3,000–6,000 3,200 Warm white (yellowish) 100
      Fluorescent lamp Mercury line + Phosphor 52–100 (white) 8,000–20,000 2,700–5,000 * White (various color temperatures), as well as saturated colors available 15–85
      Metal-halide lamp Quasi-continuous 50–115 6,000–20,000 3,000–4,500 Cold white 65–93
      Sulfur lamp Continuous 80–110 15,000–20,000 6,000 Pale green 79
      High pressure sodium Broadband 55–140 10,000–40,000 1,800–2,200 * Pinkish orange 0–70
      Low pressure sodium Narrow line 100–200 18,000–20,000 1,800 * Yellow, no color rendering 0
      LED lamp Line plus phosphor 10–200 [7] (white) 50,000–100,000 Various white from 2,700 to 6,000 * Various color temperatures, as well as saturated colors 70–85 (white)
      Electrodeless lamp Mercury line + Phosphor 70–90 (white) 80,000–100,000 Various white from 2,700 to 6,000 * Various color temperatures, as well as saturated colors 70–85 (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 Edit

      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 Edit

      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 Edit

      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. [8] 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. [9]

      LED lamp Edit

      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 Edit

      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 Edit

      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 little 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 Edit

      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.

      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.

      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.

      The History of the Light Bulb

      Ask the question: &lsquoWho invented the light bulb?&rsquo and chances are people will say Thomas Edison. Yet whilst it&rsquos certainly true that the American inventor created a commercially viable incandescent bulb, many others had put a lot of, er, &lsquoenergy&rsquo into the invention of electric light before him. To tell you more, Socket Store has compiled this not-so-brief history of the light bulb!

      1802: For some time, inventors had been trying to convert electricity into light and finally a British chemist called Thomas Davy succeeded after creating an electric version of the recently invented battery. By attaching wires and a piece of carbon to his battery, he was able to generate a small but very bright light. His &lsquoelectric arc lamp&rsquo was much too bright and the light didn&rsquot last for long &ndash but he had invented electric incandescent lighting and paved the way for Edison.

      1815: Davy studied gases, and a group of miners from Newcastle wrote to tell him of the dangers they faced of underground explosions, caused when their candles sparked methane gas. Davy invented a safety light called the Davy lamp later that year engineer George Stephenson also produced a safety lamp.

      1840: Another British scientist, Warren de la Rue, invented a glass bulb with a platinum coil inside, which lit up when an electric current was passed through it. De la Rue&rsquos light was efficient and lasted longer than Davy&rsquos, but platinum was too expensive to be used commercially.

      1850: Joseph Swan was another English scientist keen to find a long-lasting light source. He started to develop a glass bulb using carbonised paper filaments but it was to be another decade before he had a working prototype.

      1860: Swan obtained a British patent for a partial vacuum, carbon filament incandescent lamp. But the lack of a good vacuum and an adequate supply of electricity meant his device had too short a span to be truly effective.

      1874: A patent was filed in Canada by Henry Woodward, a Toronto medical electrician, and Mathew Evans. Their lamps, made in different sizes and containing carbon rods held between electrodes in nitrogen-filled bulbs, worked well, but they couldn&rsquot convert their idea into a successful business.

      1878: The development throughout the 1870s of better vacuums had allowed Swan to improve his light and, in 1878, he gave the first public demonstration of his incandescent carbon lamp in Newcastle. But, after burning brightly for a few moments, the lamp broke down due to excessive current!

      1879: On January 17, Swan successfully repeated the demonstration after refining his invention. His bulbs began to appear in homes throughout England, including Cragside in Northumberland, the first house in the world to be lit by hydroelectricity!

      Meanwhile, on the other side of the Atlantic, Woodward and Evans had sold their patent to a certain Thomas Edison, an American inventor researching the development of a practical incandescent lamp. He experimented with thousands of filaments and discovered a carbon variety that could glow for up to 40 hours in an oxygen-free bulb without burning out. Edison continued to improve his bulb until he produced a bamboo filament version capable of emitting light for more than 1,200 hours. This became the standard for the next decade &ndash during which time he also invented the Edison screw, which today remains the standard socket fitting for light bulbs!

      1880: The Edison Electric Light Company began to market the incandescent light bulb.

      1901: An American inventor called Peter Cooper-Hewitt created a mercury vapour lamp that was to become the direct forerunner of the fluorescent bulb. Despite radiating lots of blue and green light and hardly any red, Cooper-Hewitt&rsquos arc lamp was extremely popular due to its efficiency he claimed it was eight times as efficient as an incandescent bulb. However, within a few years his mercury bulb was falling behind the huge advances in incandescent lighting&hellip

      1906: Edison had long ago realised that tungsten would make the best filament but didn&rsquot have the technology to develop his idea. The General Electric Company eventually patented a method of making tungsten filaments and refined their invention over the next few years.

      1919: General Electric bought out the Cooper-Hewitt Company.

      1927: A Russian radio technician called Oleg Losev published details of the first light emitting diode (LED) in a Russian journal after noticing that diodes used in radio receivers gave out light when a current ran through them.

      In the same year, Berlin-born Edmund Germer patented a fluorescent lamp and in the 1930s developed a high-pressure variant of Cooper-Hewitt&rsquos vapour arc lamp. His original low-pressure lamps had emitted large amount of ultra-violet light but Germer and his colleagues worked out that by coating the inside of the light bulb with a fluorescent chemical, the UV light would be absorbed and the energy re-radiated as visible light. The lamp therefore provided a more economical light with less heat.

      1938: By now, GE had bought Germer&rsquos patent and a group of scientists had improved his fluorescent light, leading to the first lamps being sold.

      1962: The first red luminescence diode, developed by American Nick Holonyak, went on sale.

      1971: Green, orange and yellow LEDs were produced &ndash although the blue LED was to elude scientists for a further two decades.

      1993: Shuji Nakamura from Japan developed the first blue LED, essential for producing white LEDs - which he later designed too.

      1995: The first white LEDs went on sale.

      2006: LEDs with more than 100 lumens per watt were produced.

      2014: Professor Nakamura, along with Professors Isamu Akasaki and Hiroshi Amano won the Nobel prize for physics in recognition of their breakthrough work on the blue LED. Professor Holonyak, now in his 80s, questioned why the work of his team had been overlooked.

      The Final Product

      Edison was able to produce over 13 continuous hours of light with the cotton thread filament, and filed his first light bulb patent on January 27, 1880. Later, he and his researchers found that the ideal filament substance was carbonized bamboo, which produced over 1,200 hours of continuous light. The first large-scale test of Edison's lights occurred September 4, 1882 when 25 buildings in New York City's financial district were illuminated.

      "The electric light has caused me the greatest amount of study and has required the most elaborate experiments," Edison later wrote. "I was never myself discouraged, or inclined to be hopeless of success. I cannot say the same for all my associates."

      Watch the video: Συνδεσμολογια Λαμπτηρων Φθορισμου