89 Fun Facts About Light Bulb

How does an incandescent light bulb produce light?

By heating a filament until it glows: in open air the white-hot wire would burn out almost at once, which is why it has to be sealed inside the glass bulb.

Which toy, launched by Kenner in 1963, was powered by two ordinary 100-watt light bulbs?

Easy-Bake Oven cakes cooked on waste warmth, since an incandescent bulb gives off far more heat than light; Kenner chose bulbs over a heating element to calm fears of burnt fingers.

Which unit, printed on modern bulb packaging, measures how much light a lamp actually gives off?

Lumens count the light itself, while watts only measure the power drawn, so wattage stopped being a guide to brightness once far more efficient lamps arrived.

In the early 1800s Humphry Davy made incandescent light by passing current through a strip of which costly metal?

Platinum glowed when Davy ran current through a thin strip of it, but the strips soon failed, and it took other experimenters more than 75 years to turn the idea into a practical bulb.

Which electric light, shown by Humphry Davy in the early 1800s, proved so bright it suited lighthouses rather than homes?

The carbon arc lamp made its light from a spark leaping between two carbon rods, so fierce and power-hungry that it stayed in railway stations, big stores and other large spaces.

Before electric spotlights, nineteenth-century theatres lit their stars by heating a block of which substance until it glowed?

Quicklime glowing in a jet of burning oxygen and hydrogen was the original limelight, which is why anyone at the centre of public attention is still said to be in it.

Which country's official citizenship guide credits Mathew Evans and Henry Woodward, not Edison, with inventing the light bulb?

Canada's guide says the pair, who built their lamp in Toronto and patented it in 1874, invented the first electric light bulb and then sold the patent to Edison, who made it famous.

Joseph Swan began experimenting in 1850 with filaments made from what, sealed in an evacuated bulb?

Carbonised paper burned out fast in the poor vacuums of the 1850s, so Swan's lamp stalled for years until better pumps let him return to it in the 1870s.

Which London playhouse became the first public building lit entirely by electricity in 1881?

The Savoy's manager, Richard D'Oyly Carte, showed the audience the lamps were safe by wrapping one in muslin and breaking it on stage: it went out without even singeing the cloth.

The first street in the world lit by incandescent bulbs was Mosley Street, in which English city where Joseph Swan worked?

Newcastle upon Tyne was Swan's proving ground: he showed his lamp to 700 people at its Literary and Philosophical Society in February 1879, and the same lamps lit Mosley Street.

Edison's breakthrough lamp of October 1879 burned for over half a day on a carbonised filament of what?

Cotton thread, the ordinary sewing kind baked to carbon, gave Edison his first lamp that lasted; accounts put the run at 13.5 or 14.5 hours, and within a year his filaments were lasting hundreds.

Which plant material did Edison's team discover made a filament lasting over 1,200 hours?

Carbonised Japanese bamboo won out after months of further trials, with Edison sending men abroad to find the best stems, and it stayed his standard filament for about ten years.

What was the first commercial application of Edison's incandescent lamps, in 1880?

A steamship, the Columbia, came first because her owner Henry Villard saw Edison's New Year's Eve demonstration and insisted on the lights for his new ship, despite Edison's own reluctance.

Historians credit Edison's success over rival bulb-makers less to his lamp than to what?

Building a whole lighting system set Edison apart: he supplied the generators, mains and wiring too, while rivals with lamps just as good had no network to plug them into.

Which Black American inventor patented an improved process for making carbon filaments in 1882?

Lewis Latimer had already made his mark as a draftsman: in 1876 he drew the patent drawings for Alexander Graham Bell's telephone, before turning to electric light.

The name 'tungsten', the metal in most bulb filaments, comes from Swedish words meaning what?

Heavy stone is the literal Swedish, but German speakers call the same metal wolfram, which is why its chemical symbol is W rather than T.

What did research published in 2007 conclude about Heinrich Göbel's claim to have built a light bulb in 1854?

The story is fictitious, the study found: the claim was pressed in 1893 as a courtroom defence for lamp makers Edison's company was suing, and the patent expired before any final ruling.

Sándor Just and Franjo Hanaman's tungsten filament of 1904 was put on sale by Tungsram, a company from which country?

Hungary's Tungsram, based in Budapest, put the lamp on the market; its tungsten wire burned brighter and lasted longer than carbon, the biggest change to the bulb since Edison.

After making tungsten workable for bulb filaments, William Coolidge invented the modern what?

X-ray tube: he put his workable tungsten into that too, and the Coolidge tube soon replaced earlier designs and became the pattern for the X-ray tubes made since.

Why is tungsten the ideal filament metal?

It has the highest melting point of any metal, above 3,400 °C, so a tungsten filament can glow white-hot for hundreds of hours without melting.

In 1913 Irving Langmuir found that filling a bulb with what, instead of a vacuum, doubled its efficacy?

An inert gas such as argon went against his colleagues' hunch that a better vacuum was the answer: the gas slowed the tungsten boiling off the filament and blackening the glass.

Marvin Pipkin's 1925 patent for General Electric solved which light-bulb problem?

Frosting a bulb's inside without weakening it mattered because earlier acid-etched bulbs turned brittle and broke in ordinary handling; his finish softened the bare filament's glare and stayed strong.

The Phoebus cartel of 1925–1939 is commonly cited as an early example of what?

Planned obsolescence: Osram, Philips and the other members agreed to cap bulb life at 1,000 hours, had sample lamps tested, and fined any factory whose bulbs burned longer.

The Phoebus cartel was incorporated in which city in January 1925?

Geneva was where the lamp makers met in December 1924 and set up Phoebus S.A. weeks later; the pact was meant to run until 1955 but fell apart when war broke out in 1939.

The Centennial Light, a bulb burning almost continuously since 1901, hangs in a fire station in which California city?

Livermore gave the bulb a full police and fire-truck escort when its firehouse moved in 1976, and since then it has run on its own protected power supply.

After more than a century, the Centennial Light, once a 60-watt bulb, glows about as brightly as what?

A 4 W nightlight is about its level now; when its backup power failed in 2013, viewers on its webcam thought it had finally burned out, but it came back on.

In the Edison screw designation E27, what does the number stand for?

The base diameter in millimetres, so an E27 cap is 27 mm across; the E is for Edison, whose screw fitting beat the incompatible bases of rival lamp makers to become the standard.

A halogen lamp is a tungsten-filament bulb whose gas fill contains a small amount of which elements?

Iodine or bromine vapour catches the tungsten that boils off the filament and carries it back, so the lamp can run hotter and brighter without its glass blackening.

Halogen lamp capsules run so hot they are often made of what instead of ordinary glass?

Quartz can take the heat, but oil from a fingertip leaves a hot spot that can crack it, which is why you are told never to handle a halogen bulb with bare hands.

In fluorescent lighting, glowing mercury vapour gives off what, which a coating on the glass then turns into visible light?

Ultraviolet is invisible, so the phosphor coating soaks it up and glows white; the same lamp made without the coating, in glass that lets the rays out, is a germicidal lamp for killing bacteria.

GE engineer Edward Hammer invented the spiral compact fluorescent lamp in 1976 in response to what?

The 1973 oil crisis set Hammer the task and his spiral tube worked, yet GE shelved it because tooling up to make it cost too much, and rivals later copied the design.

Georges Claude lit up the 1910 Paris Motor Show with glowing tubes of which gas, a by-product of his liquid-air business?

Neon was left over whenever Claude's company liquefied air, so he put it to work, and his glowing red tubes went on to become the classic advertising sign.

Low-pressure sodium lamps, long used for street lighting, give off light of what colour?

Yellow-orange is the only colour they give out, which makes them among the most efficient lamps ever built but leaves everything beneath them looking the same washed-out shade.

British engineer Henry Round first saw a crystal glow under electric current in 1907 while working for which company?

Marconi's radio man Henry Round was probing a carborundum crystal with a cat's-whisker wire when it glowed, and he reported it in a brief note; practical LEDs took another half-century.

The earliest practical LEDs of 1962 emitted what kind of light?

Low-intensity infrared came first, and it has never left: invisible infrared LEDs still send the signals from television remote controls.

Which General Electric scientist demonstrated a red LED in 1962, a first step towards today's LED lamps?

Nick Holonyak's glowing red device of 1962 led to the first commercial LEDs, and he lived until 2022, long enough to see LED lamps push Edison's bulb off the shelves.

Shuji Nakamura shared the 2014 Nobel Prize in Physics with Akasaki and Amano for inventing what?

The blue LED was the missing colour: red and green ones had existed for decades, and only with blue could LEDs make the white light that now fills lamps and screens.

Nakamura developed the high-brightness gallium nitride LED while working for which Japanese company?

Nichia rewarded Nakamura with just 20,000 yen, about $180, for an invention that transformed the company; he later sued it and settled for 840 million yen.

The finned metal body on many LED bulbs is there to do what?

Carry heat away: an LED still makes some heat, and the hotter it runs the faster its light fades and the sooner it fails, so the metal body soaks the heat up and sheds it into the air.

Which Caribbean country handed out CFLs to replace every incandescent bulb, then banned the old bulbs' sale in 2006-07?

Cuba exchanged about 9.4 million old bulbs for energy-saving lamps during its 'Energy Revolution', which also handed out millions of fans, refrigerators and rice cookers.

In 2009 the EU estimated its ban on incandescent bulbs would save as much electricity each year as which country uses?

Romania's yearly electricity use, close to 40 terawatt-hours, was the Commission's yardstick; it reckoned the ban would spare the output of ten power stations and 15 million tonnes of CO2 a year.

What glowing element let Walther Nernst's 1897 lamp burn in open air, with no vacuum at all?

A ceramic rod cannot burn away because it is already an oxide, so it needed no vacuum, but it only conducted when hot and had to be warmed by a separate heater before it would light.

Before electric light, William Murdoch lit his Cornish home in the 1790s by burning what?

Coal gas made Murdoch's house in Redruth the first home lit by gas, and within decades gaslight had spread to the streets, homes and factories of Europe and North America.

Edison's facility, considered the first industrial research lab, was where in New Jersey?

Menlo Park is where Edison first showed his lamps to the public, lighting up the laboratory on New Year's Eve 1879; by then the press already called him its Wizard.

In the name LED, what does the letter D stand for?

Diode: a one-way gate for current, and because a light-emitting one makes light directly as current crosses it, an LED lamp needs only a fraction of an incandescent bulb's power.

Which lamp, first sold in 1938, soon took over offices and factories by using far less power than a filament bulb?

The fluorescent tube gave two to three times the light per watt, and wartime factories adopted it so fast that by 1951 it was producing more of America's light than filament bulbs.

In 1930, physicist Imre Bródy made bulbs more efficient by filling them with which rare gas?

Krypton atoms are heavy, so they slow the filament's evaporation and carry away less heat, but the gas was scarce and costly, so Bródy also devised a way to extract it from air.

Hakunetsu-sha, a Tokyo light-bulb maker founded in 1890 by the 'Japanese Edison' Ichisuke Fujioka, grew into which electronics giant?

Toshiba was born in 1939 when the bulb maker, by then called Tokyo Electric, merged with the Shibaura engineering works; the name joins the opening sounds of Tokyo and Shibaura.

Why are bayonet-base bulbs frequently used in automotive lamps?

They resist loosening from vibration because the bulb's pins lock into slots with a push and a twist, the way a bayonet clips to a rifle; the weapon is named after Bayonne in France.

Which Addams Family character can light up a bulb simply by putting it in his mouth?

Uncle Fester does it with a loud crackling noise, a party trick that dates back to the 1964 television series, in which Jackie Coogan played him.

Which 1937 Picasso painting shows a bare light bulb blazing like an all-seeing eye above a wounded horse?

Guernica was painted for Spain's pavilion at the 1937 Paris world's fair, and one common reading takes its harsh electric bulb to stand for the sun.

Which British novelty of 1963 relies on the warmth of an ordinary bulb to keep blobs of wax rising and falling?

The lava lamp came to Edward Craven Walker after he watched a homemade egg timer, built from a cocktail shaker, bubbling away on a pub stove.

In theatre tradition, what name is given to a lone bare bulb left burning on an empty stage overnight?

Ghost light is the name, and although its real job is to stop people falling into the orchestra pit, superstition says it lets a theatre's resident spirits perform.

One hundred incandescent bulbs lit the first New Year's Eve ball, lowered in 1907 at which New York landmark?

Times Square got its ball because newspaper owner Adolph Ochs wanted a bigger spectacle after the city banned his rooftop fireworks; the iron-and-wood sphere weighed 700 pounds.

Hiram Maxim, who fought Thomas Edison over light-bulb patents, is far better known for inventing which weapon?

The machine gun made Maxim's name after he moved to Britain, yet he always claimed that he, not Edison, was the true inventor of the light bulb.

Which European electronics giant began in 1891 as an Eindhoven factory making incandescent light bulbs?

Philips was founded by Gerard Philips and his father Frederik, and the sports club it set up for its workers in 1913 lives on as the football team PSV Eindhoven.

After the EU banned incandescent bulbs, a German importer tried to keep selling them by relabelling them as what?

Mini heaters was the label, under the brand name Heatballs, a dig at how much of a filament bulb's power turns to warmth; the ruse was banned shortly afterwards.

What happened to members of the 1920s Phoebus cartel whose light bulbs lasted longer than 1,000 hours?

They were fined after the cartel tested samples of their bulbs, on a scale in Swiss francs that rose the longer a bulb outlasted the limit.

Which German lamp maker's name blends wolfram, German for tungsten, with a second filament metal?

Osram was registered as a brand in 1906 for a lamp developed by Carl Auer von Welsbach, and both metals in its name were being used for filaments at the time.

Which light-bulb brand, launched by General Electric in 1909, was named after the supreme god of Zoroastrianism?

Mazda honours Ahura Mazda, whose name pairs the Avestan words for lord and wisdom, though today most people link the word with a Japanese carmaker instead.

Why do makers warn against touching the capsule of a halogen bulb with bare fingers?

Skin oil can make it fail because the smear soaks up more warmth than clean glass, creating a hot spot on the envelope once the lamp is switched on.

What does a three-way incandescent bulb contain that lets a single lamp shine at three different brightness levels?

Two separate filaments, one fainter than the other, can be lit alone or together to give three levels; versions for the home were on sale by 1935.

Labels such as 'warm white' and 'daylight' on a bulb box describe its colour temperature, measured in which unit?

Kelvins run opposite to instinct here: bulbs of 2,700 to 3,000 K are the ones called warm, while bluish light above 5,000 K is called cool.

Which US president signed the energy law that set America's phase-out of traditional incandescent bulbs in motion?

George W. Bush signed the Energy Independence and Security Act in December 2007; it named no bulb, but set power limits that the old filament designs could not meet.

When Thomas Edison died in 1931, President Hoover asked Americans to pay tribute by doing what for one minute?

Switching off their lights was set for the evening of October 21; Hoover turned down a plan to cut the current at the generating plants because it would have put lives at risk.

Which carmaker staged Light's Golden Jubilee in 1929, the light bulb's fiftieth birthday party, at his Michigan museum?

Henry Ford, a long-time friend of Edison, won control of the party from General Electric and moved it to Dearborn, where his Greenfield Village was dedicated the same day.

Before wall outlets became common, how were early electric appliances usually connected to a home's power supply?

Via a light bulb socket, using a plug that screwed in where the bulb went; some homes kept the habit because power on lighting circuits was billed at a lower rate.

Which company lit the 1893 Chicago World's Fair with a 'stopper' lamp designed to sidestep Edison's bulb patent?

Westinghouse underbid Edison General Electric by 70 cents a lamp, then dodged the patent on a sealed glass globe by closing each bulb with a ground-glass stopper.

Edison's first commercial power station began lighting 400 lamps in lower Manhattan in 1882 from which address?

Pearl Street housed six steam-driven dynamos that started up on September 4, 1882; within two years the plant was feeding more than 10,000 lamps.

Cragside, the Northumberland mansion fitted with Joseph Swan's lamps in 1880, was the first house lit by what?

Water power from dammed lakes on the estate turned a dynamo for William Armstrong, the arms maker who made Cragside the first house lit by hydroelectricity.

Edison's study of why his bulbs blackened inside revealed an effect that later made possible which electronic component?

The vacuum tube grew out of the 'Edison effect', a one-way current crossing the empty space inside a bulb, which John Ambrose Fleming turned into a radio-wave detector in 1904.

Which US president had electricity installed in the White House but reportedly feared touching the light switches?

Benjamin Harrison and his wife were so afraid of electrocution that they often went to sleep with the lights still on after Edison's company wired the mansion.

Which gas fills the dazzling white lamps that cinemas adopted for projecting films from the 1950s?

Xenon lamps imitate sunlight, and the first public film show to use one took place in Berlin in 1950; the largest dome screens later needed lamps rated at 15 kilowatts.

When webcam viewers saw the Centennial Light go dark in 2013, what had actually failed instead of the bulb?

Its dedicated power supply had cut out, and the bulb came straight back to life when it was run from an ordinary extension cord instead.

Why were light bulbs on the New York City Subway long made with left-hand screw threads?

To discourage bulb theft: a lamp unscrewed from a train simply would not fit the ordinary right-hand fittings in anyone's home.

Early bulb makers pumped the air out of the glass chiefly to keep which gas away from the white-hot filament?

Oxygen eats away a hot filament, and even a trace of moisture left in a bulb splits apart when the lamp is lit and releases enough of it to do damage.

The everyday German word for a light bulb, Glühbirne, literally compares its shape to which fruit?

Pear is the meaning of Birne, so a German Glühbirne is literally a pear that shines, a nod to the outline of the classic household bulb.

Which inventor amazed audiences in the 1890s by lighting bulbs from across a stage with no wires attached?

Nikola Tesla fed the lamps through the air with high-voltage, high-frequency current from his own coil design, and hoped to send power around the world the same way.

On a traditional light bulb, what does a rating such as '60 W' actually measure?

The power it consumes is all the watt figure records, so two lamps drawing the same wattage can differ enormously in brightness depending on how they make light.

What causes the glass of an ageing incandescent bulb to darken gradually on the inside?

Evaporated filament metal condenses on the cooler glass, and in a gas-filled bulb convection carries it upwards, so only the top of the envelope turns black.

In Disney's Duck comics, which inventor is assisted by Little Helper, a tiny robot with a light bulb for a head?

Gyro Gearloose, created by Carl Barks in 1952, is Duckburg's resident inventor, and despite the company he keeps he is drawn as a chicken, not a duck.

Which lighting control did Joel Spira shrink to fit a household wall box in 1959, before founding Lutron Electronics?

The dimmer had relied on rheostats that threw away much of the power as warmth; Spira's version used a new solid-state part, the silicon controlled rectifier.

Which American glassmaker's 'Ribbon' invention of 1926 automated bulb-blowing so well it was still in use this century?

Corning managed about 150 hand-blown bulbs an hour in the 1880s; by the 1970s just fifteen ribbon machines were turning out the world's entire supply of bulb glass.

Unwound and stretched straight, the coiled tungsten filament of a 60-watt, 120-volt bulb would measure roughly how long?

About 58 cm of wire just 0.046 mm thick is wound into a coil, and often into a coil of coils, so that it fits inside an ordinary bulb.

The oversized E39 screw base used on North American street lights and high-power lamps goes by which grand name?

Mogul is the North American name, while Europe's near-identical E40 fitting is known as the Goliath; ordinary household bulbs use the size called medium.

Byron the Bulb, an immortal light bulb who battles the Phoebus cartel, appears in which Thomas Pynchon novel?

Gravity's Rainbow has been credited with bringing the real-life bulb makers' cartel to public attention; Byron's tale is one of the novel's long digressions.

Thomas Edison is said to have modelled his light bulb's screw base on the threaded lid of what workshop container?

A kerosene can supplied the idea, the story goes, with Edison sawing off its lid to build a prototype in 1880: a borrowing from the very lamp fuel his bulbs would replace.

Which European landmark was fitted with 20,000 bulbs to sparkle for five minutes every hour as the year 2000 arrived?

The Eiffel Tower's sparkle was put up for the millennium and went dark in July 2001, but the bulbs were switched back on in June 2003.

Edison's associate Edward Johnson hand-wired 80 red, white and blue bulbs in 1882 to light the first electric what?

Christmas tree lighting began at Johnson's New York home with bulbs the size of walnuts, and he is now regarded as the father of electric tree lights.