Exam-style question
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Which of the following statements correctly applies sign conventions in thermodynamics?.
- A.Heat added to a system is positive, while work done by the system is negative.
- B.Work done on a system is positive, while heat removed from the system is positive.
- C.Heat removed from a system is negative, while work done on the system is negative.
- D.Heat added to a system is negative, while work done on the system is positive.
Model answer
What a good answer should say
- Heat added to a system is positive, while work done by the system is negative.
Explanation
Why this works
In thermodynamics, the sign convention states that heat added to a system is considered positive, while work done by the system (expansion work) is considered negative. This helps in correctly applying the first law of thermodynamics.
Common mistake
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