Question

A heat engine can reach 100 percent efficiency only if waste heat is transferred to an environment at what temperature?

a) Absolute zero
b) Room temperature
c) Boiling point
d) Freezing point

Answer 1

A heat engine can only reach 100 percent efficiency if waste heat is transferred to an environment at absolute zero, but achieving absolute zero is not possible in any real heat engine.

Step-by-step explanation:

A heat engine can reach 100 percent efficiency only if waste heat is transferred to an environment at absolute zero. Carnot's result shows that the only way to have all heat transfer go into doing work is to remove all thermal energy, which requires a cold reservoir at absolute zero. However, achieving absolute zero is both a practical and theoretical impossibility. Therefore, 100 percent efficiency is not possible in any real heat engine.