SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/eng-carnot-efficiency-limit

What is the maximum ideal efficiency between reservoirs at Th and Tc?

Carnot efficiency is 1 - Tc/Th, using kelvins.

Start playing free

  1. 1 - Tc/Th ✔
  2. 1 - Th/Tc
  3. Tc/Th

Why: A reversible Carnot engine sets the upper efficiency limit between two temperatures. Both temperatures must be absolute, so engineers use kelvins in the ratio.

Huh, didn't know that: No real engine between the same reservoirs can exceed the reversible Carnot limit.

The dad joke
Carnot set the efficiency ceiling, and every real engine works below it.
Like this card?
Play the game

References

Answer: 1 - Tc/Th. A reversible Carnot engine sets the upper efficiency limit between two temperatures. Both temperatures must be absolute, so engineers use kelvins in the ratio.

  1. OpenStax University Physics Volume 2, The Carnot Cycle openstax.org/books/university-physics-volume-2/pages/4-5-the-carnot-cycle
    the efficiency of this ideal gas Carnot engine is given by e=1-Tc/Th
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

EngineeringHow many base units does the International System of Units (SI) have?EngineeringSince the SI redefinition voted in 2018, what defines the kilogram?EngineeringIn today's SI, how precisely is the value of the Planck constant known?

That's stuff everyone should know.