Exam-style question
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Why is no heat engine perfectly efficient?.
- A.Some energy is always lost as waste heat.
- B.All energy is converted to work.
- C.Heat engines operate at constant temperature.
- D.Heat engines require no energy input.
Model answer
What a good answer should say
- Some energy is always lost as waste heat.
Explanation
Why this works
This option highlights the reality that in any real heat engine, some energy is inevitably lost to the surroundings as waste heat, preventing 100% efficiency.
Common mistake
No common mistake is linked to this question yet.