Exam-style question
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Explain why no heat engine is perfectly efficient.
Model answer
What a good answer should say
- No heat engine is perfectly efficient because some energy is always lost as waste heat to the surroundings during the energy conversion process.
- This occurs due to the second law of thermodynamics, which states that energy transformations are not 100% efficient.
- As a result, the useful work output is always less than the energy input, leading to inefficiencies in the system.
Explanation
Why this works
This answer is strong because it identifies the cause (energy loss as waste heat), explains the mechanism (second law of thermodynamics), and states the effect (useful work output is less than energy input) along with the consequence (inefficiencies in the system). The question tests understanding of thermodynamic principles.
Common mistake
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