A heat engine could be 100% efficient only if:

  1. both reservoirs were at the same temperature
  2. the cold reservoir were at absolute zero
  3. the hot reservoir were at 0 K
  4. there were no friction
Answer

B) the cold reservoir were at absolute zero

Impossible in practice. SLO P-11-C-23 · Knowledge

Physics MCQ · More Heat Engines, Second Law and Entropy MCQs · Practise