Getting your questions ready
Getting your questions ready
Beat the crowd
10 questions No timer
50 free Kelvin trivia questions with answers — science & nature quiz, new questions added Aug 2026.
Kelvin is both a unit and a man, and this quiz covers both. On the unit side: why the scale starts at absolute zero, why you add 273.15, why the triple point of water was 273.16 K for 65 years, what the Boltzmann constant has to do with the 2019 redefinition, why 'degree Kelvin' was abolished, how the Rankine scale differs, and what 5772 K means when you point a camera at the Sun. On the man: the Belfast boy who entered Glasgow University at ten, the 1848 paper that proposed an absolute scale, the Carnot cycle and James Joule, the mirror galvanometer that saved the Atlantic telegraph and earned him a knighthood, the marriage proposal by signal flag, the compass, the water dropper, the wake pattern, the doomed 20-to-40-million-year estimate for the age of the Earth, and the seat in Westminster Abbey next to Newton. Every answer was checked against Wikipedia's articles on the kelvin, absolute zero, Lord Kelvin and the transatlantic cable, and the supporting sentence is attached to each question. For the wider field, try our Physics quiz.
30 of 50 questions with answers and explanations. Play the quiz
Q 01The kelvin is the base unit of temperature in which set of units?
The International System (SI)
It is one of seven SI base units, and the only one whose scale starts at a true physical zero.
Q 02What is the symbol for the kelvin?
K
'Degree Kelvin' with the ° sign was officially dropped in 1967–68.
Q 03What do you add to a Celsius temperature to convert it to kelvins?
273.15
A one-kelvin step and a one-degree-Celsius step are exactly the same size.
Q 04What temperature does 0 K represent?
Absolute zero
It is the lowest possible temperature, the point at which classical particle motion would stop.
Q 05What was Lord Kelvin's name before he was ennobled?
William Thomson
He was knighted in 1866 and became a baron in 1892.
Q 06In which city was the future Lord Kelvin born?
Belfast
His father taught mathematics there before moving the family to Glasgow in 1833.
Q 07At what age did the young Thomson start studying at the University of Glasgow?
10
Not precocity: the university then provided an elementary education for able boys, and 10 was a normal starting age.
Q 08For how many years was Kelvin professor of Natural Philosophy at Glasgow?
53
He refused offers from world-famous universities and stayed until retiring in 1899.
Q 09At which Cambridge college did Thomson study, becoming a fellow in 1845?
Peterhouse
He then worked in Regnault's Paris laboratory before taking the Glasgow chair at 22.
Q 10Kelvin's title refers to what natural feature near his Glasgow laboratory?
A river
His title was Baron Kelvin of Largs, the Ayrshire town where he built his mansion Netherhall.
Q 11In what year did Thomson publish 'On an Absolute Thermometric Scale'?
1848
In a footnote he derived −273 °C for the bottom of the scale from the thermal expansion of gases.
Q 12Which physicist worked with Thomson through the 1850s on the formula behind the absolute scale?
James Prescott Joule
He was named after the same man as the SI unit of energy; Thomson's Carnot function turned out to be a constant.
Q 13Kelvin's scale was built on the theoretical heat engine of which French engineer?
Sadi Carnot
His idealised reversible cycle links the ratio of heat taken in and rejected to the ratio of absolute temperatures.
Q 21Which SI derived unit is the only one with a special name derived from the kelvin?
The degree Celsius
Metric prefixes work too: a millikelvin is a thousandth of a kelvin.
Q 22According to SI style rules, how should the unit's name be written in running text?
Lower case: 'kelvin'
The symbol K is capitalised because it comes from a person's name, and 283 kelvins is the correct plural.
Q 23Which absolute temperature system uses Fahrenheit-sized degrees instead of Celsius-sized ones?
The Rankine scale
It was proposed in 1859 by another Glasgow professor, W. J. M. Rankine.
Q 14In the early 20th century, the Kelvin scale went by which nickname?
Absolute Celsius
People even used the °C symbol for it, just counting from the bottom of the scale.
Q 15Which of Kelvin's relatives coined the term 'triple point' in 1873?
His older brother James
At a substance's triple point, solid, liquid and gas coexist at one unique temperature and pressure.
Q 16From 1954 to 2019, the kelvin was defined so that the triple point of water was exactly what?
273.16 K
That is 0.01 °C; the triple point was preferred to the melting point because it could be measured ten times more precisely.
Q 17What change did the 13th CGPM make to the unit in 1967–68?
Renamed 'degree Kelvin' (°K) to 'kelvin' (K)
Since then the SI convention has been that the kelvin is never written or spoken as a 'degree'.
Q 18The 2019 redefinition of the kelvin fixed the exact value of what?
The Boltzmann constant
Every 1 K change now corresponds to exactly 1.380649×10⁻²³ joules of thermal energy.
Q 19On what date did the 2019 redefinition of the kelvin come into force?
20 May 2019
It was the 144th anniversary of the Metre Convention, and the change went almost unnoticed in daily life.
Q 20After 2019, where did the measurement uncertainty that used to sit on kB move to?
It moved to the triple point of water
The triple point of water is now 273.1600(1) K rather than exact.
Q 24Below roughly what colour temperature do black-body light sources look reddish?
About 4000 K
Above about 7500 K they look bluish; daylight film wanted about 5600 K.
Q 25What effective temperature does the IAU adopt for the Sun's photosphere?
5772 K
The colour temperature of sunlight above the atmosphere is about 5,900 K.
Q 26In photography, what does raising the colour temperature setting do to an image?
Enhances white and blue hues
Lowering it makes the picture more dominated by reddish, 'warmer' colours.
Q 27In electronics, the kelvin is used to express what property of a circuit?
Its noise temperature
Johnson–Nyquist noise in resistors is thermal noise tied to kB.
Q 28The Unicode 'Kelvin sign' (U+212A) exists, but what does the Unicode standard recommend using instead?
The ordinary capital letter K
The Ohm sign and Angstrom sign are the other two 'letterlike symbols' with the same advice.
Q 290 K corresponds to what temperature in Fahrenheit?
−459.67 °F
Nothing can be cooled to it, but Bremen physicists reached 38 trillionths of a kelvin above it in 2018.
Q 30Who first raised the question of a lowest possible temperature in 1703, while improving the air thermometer?
Guillaume Amontons
Extrapolating gas volume to zero later pointed to about −273 °C.