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50 free Light Bulb trivia questions with answers — technology quiz, new questions added Aug 2026.
The light bulb is the classic symbol of a bright idea, and its real history is far messier than the Edison legend. This quiz covers the whole story: Humphry Davy's glowing platinum strip in 1802, the forgotten patents of the 1840s, Joseph Swan's Newcastle demonstrations, Edison's bamboo filament and his integrated lighting system, Lewis Latimer's carbon process, the switch to tungsten and inert gas, the cartel that fixed bulb life at 1,000 hours, the fire-station bulb that has burned since 1901, and the modern age of halogen, fluorescent, sodium, neon and LED lighting up to the Nobel Prize for the blue LED and the bans on incandescents. Easy questions ask what a filament is made of and who founded Menlo Park; harder ones cover the Hungarian tungsten patent, the E in E27 and how much of a bulb's energy becomes light. It suits science and technology students, engineers, history buffs and quiz nights that want a science round rooted in everyday objects. Every answer has been checked against the Wikipedia articles on incandescent, fluorescent, halogen and LED lighting and the people behind them, and each question shows its source once you have answered.
30 of 50 questions with answers and explanations. Play the quiz
Q 01How does an incandescent light bulb produce light?
By heating a filament until it glows
The filament sits in a bulb that is either evacuated or filled with inert gas to stop it oxidising.
Q 02Roughly what share of the energy consumed by an incandescent bulb becomes visible light?
Less than 5 percent
The rest is released as heat, which is why they work as heat lamps for incubators and Easy-Bake Ovens.
Q 03What is the luminous efficacy of a 120-volt incandescent bulb?
16 lm/W
A compact fluorescent manages about 60, which is why governments have banned the old bulbs to save energy.
Q 04In 1802 Humphry Davy made incandescent light by passing current through a strip of which high-melting metal?
Platinum
He used a battery of 2,000 cells in the basement of the Royal Institution; it was too dim and short-lived to be practical.
Q 05What was the first practical electric light, invented by Davy in the first decade of the 1800s?
The carbon arc lamp
Arc lamps burned their carbon rods fast and gave out kilowatts of light, so they suited only large spaces.
Q 06Who was granted the first patent for an incandescent lamp, in 1841, using metal wires in a vacuum bulb?
Frederick de Moleyns
De la Rue had enclosed a coiled filament of the same costly metal in a vacuum tube the year before, but the metal's cost made it impractical.
Q 07Which country holds that Henry Woodward and Mathew Evans invented the light bulb, with an 1874 patent sold to Edison?
Canada
Their lamp used carbon rods in a nitrogen-filled glass cylinder; Edison needed their claim for lamps wired in parallel.
Q 08Joseph Swan began experimenting in 1850 with filaments made from what, sealed in an evacuated bulb?
Carbonised paper
Better vacuum pumps in the 1870s let him return to the experiments, and his lamp was in daily use in London by 1881.
Q 09Which London playhouse became the first public building lit entirely by electricity in 1881?
The Savoy
Swan's own house, Underhill in Gateshead, was the first in the world lit by a light bulb.
Q 10The first street in the world lit by incandescent lamps, in 1880, was Mosley Street in which English city?
Newcastle upon Tyne
The city's Literary and Philosophical Society building had been the first public building lit by electricity the year before.
Q 11How long did Edison's first successful carbon-filament test lamp burn on 22 October 1879?
13.5 hours
His team later found a carbonised Japanese bamboo filament could last more than 1,200 hours.
Q 12Which plant material did Edison's team discover made a filament lasting over 1,200 hours?
Carbonised Japanese bamboo
His 1879 patent had listed cotton, linen thread, wood splints and coiled paper among the possibilities.
Q 13What was the first commercial application of Edison's incandescent lamps, in 1880?
A steamship, the Columbia
Q 21Why is tungsten the ideal filament metal?
It has the highest melting point of any element
It melts at 3,422 °C, and its symbol W comes from the German name Wolfram.
Q 22In 1913 Irving Langmuir found that filling a bulb with what, instead of a vacuum, doubled its efficacy?
An inert gas such as argon
The gas slows the evaporation of the tungsten filament; Imre Bródy later used krypton.
Q 23Marvin Pipkin's 1925 patent solved which everyday problem?
Frosting a bulb's inside without weakening it
The Oregon Railroad and Navigation Company vessel was also the first ship to carry a dynamo.
Q 14Historians credit Edison's business success less to the bulb itself than to what?
Developing an entire integrated system of electric lighting
Generators, mains, feeders and parallel distribution were as vital as the lamp, which is why rivals with equally good bulbs are forgotten.
Q 15Which Black American inventor patented an improved process for making carbon filaments in 1882?
Lewis Latimer
His heat-treatment reduced breakage and let filaments be moulded into shapes like Maxim's characteristic "M".
Q 16The Edison and Swan companies merged in Britain to form a firm later known by what name?
Ediswan
Edison opposed the merger at first but was forced to cooperate, and eventually bought out Swan's interest.
Q 17In 1883 the US Patent Office ruled Edison's lamp patents invalid as based on whose prior art?
William Sawyer
A judge finally upheld Edison's claim for "a filament of carbon of high resistance" in 1889.
Q 18What did 2007 research conclude about Heinrich Göbel's claimed 1854 bamboo-filament bulb?
The story is fictitious
Four courts had raised doubts, but Edison's patent expired before a final ruling.
Q 19Which two men were granted the first patent for a tungsten-filament lamp, in Hungary in 1904?
Sándor Just and Franjo Hanaman
The Hungarian company Tungsram marketed them the same year, and Europeans still call them Tungsram bulbs.
Q 20Which General Electric scientist developed "ductile tungsten" in 1906?
William D. Coolidge
GE began selling bulbs with the ductile tungsten wire in 1911.
The frosted finish diffuses the glare of the bare filament.
Q 24The Phoebus cartel of 1925–1939 is commonly cited as an early example of what?
Planned obsolescence
Osram, Philips, GE and others fixed prices and standardised bulb life at 1,000 hours, a figure that outlived the cartel.
Q 25The Phoebus cartel was incorporated in which city in January 1925?
Geneva
It was meant to last thirty years but folded in 1939 with the outbreak of the Second World War.
Q 26The Centennial Light, the world's longest-lasting bulb, has burned almost continuously since 1901 in a fire station in which California city?
Livermore
Made by the Shelby Electric Company of Ohio, it began as a 60-watt bulb and now glows like a 4-watt nightlight.
Q 27Originally rated at 60 W, the Centennial Light has dimmed to roughly the output of what?
A 4 W nightlight
It has been turned off only a few brief times and has its own webcam.
Q 28In the Edison screw designation E27, what does the number stand for?
The base diameter in millimetres
Edison patented the screw base in 1881; his one-inch, seven-thread version became the E26 used in North America.
Q 29A halogen lamp is a tungsten-filament bulb whose gas fill contains a small amount of which elements?
Iodine or bromine
The halogen cycle redeposits evaporated tungsten on the filament, extending its life and keeping the envelope clear.
Q 30In which year did General Electric patent the first practical halogen lamp?
1959
The concept of cyclic redeposition of tungsten had appeared in a patent back in 1933.