Question 1

What is Carnot efficiency?

Accepted Answer

Carnot efficiency is the maximum theoretical efficiency any heat engine can achieve operating between two temperatures. It equals η = 1 - T_cold/T_hot where temperatures are in Kelvin. No real engine can exceed this limit.

Question 2

What is COP for a refrigerator vs heat pump?

Accepted Answer

COP (Coefficient of Performance) measures efficiency of refrigerators and heat pumps. For a refrigerator: COP = T_cold/(T_hot - T_cold). For a heat pump: COP = T_hot/(T_hot - T_cold). Both are always > 1 for ideal Carnot cycles.

Question 3

Why must temperatures be in Kelvin?

Accepted Answer

The Carnot formula requires absolute temperatures in Kelvin because it represents the thermodynamic temperature scale where 0 K is absolute zero. Using Celsius would give incorrect results since Celsius has an arbitrary zero point.

Carnot Efficiency Calculator