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QPage 60: Q12: HC Verma: Concepts of Physics - Volume 2 Laws of Thermodynamics Page 60: Q12 Solution: When we heat an object, it expands. Is work done by the object…

⚠️ Common Exam Traps & Conceptual Pitfalls

Many students assume that all heat added to a system becomes internal energy, forgetting that if the system expands, part of the heat does $PDelta V$ work. Remember the first law: $Delta Q=Delta U+PDelta V$; if $Delta V>0$, then $Delta Q>Delta U$.

When we heat an object, it expands. Is work done by the object in this process? Is heat given to the object equal to the increase in its internal energy?

Step-by-Step Verified Solution

**Answer:** Yes, work is done by the object. No, heat given is not equal to the increase in internal energy. **Step-by-Step Explanation:** When heated, the object expands, so ΔV>0\Delta V > 0 and work done by the object W=PΔV>0W = P\Delta V > 0. From the first law, ΔQ=ΔU+ΔW\Delta Q = \Delta U + \Delta W. Since W≠0W \neq 0, ΔQ≠ΔU\Delta Q \neq \Delta U. The heat supplied is shared between increasing internal energy and doing expansion work [citation:8][citation:10].

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