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Laws of Thermodynamics
GATE 2013
Medium
The thermodynamic state of a closed system containing a pure fluid changes from (T1,p1) to (T2,p2). Let Q denote the heat absorbed (>0 if absorbed by the system) and W the work done (>0 if done by the system). Neglect changes in kinetic and potential energies. Which one of the following is CORRECT?
- AQ is path-independent and W is path-dependent
- BQ is path-dependent and W is path-independent
- (Q−W) is path-independent
- D(Q+W) is path-independent
Explanation
By the first law, ΔU=Q−W. Since U is a state function, ΔU (and hence Q−W) depends only on the initial and final states, not the path — while Q and W individually are path-dependent.
Source: GATE CH 2013 (2013)
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