Exam-style question
Try this first
Why is no heat engine perfectly efficient?.
- A.Because some energy is always lost as waste heat
- B.Because all energy is converted to work
- C.Because heat engines operate at constant temperature
- D.Because they use only renewable energy sources
Model answer
What a good answer should say
- Because some energy is always lost as waste heat
Explanation
Why this works
The cause is that heat engines operate based on the conversion of thermal energy to work. The mechanism involves the second law of thermodynamics, which states that not all energy can be converted into work due to inherent inefficiencies, such as friction and heat loss.
The effect is that some energy is always expelled as waste heat, leading to the consequence that no heat engine can achieve 100% efficiency.
Common mistake
No common mistake is linked to this question yet.