A) 30 J
B) 20 J
C) 60 J
D) 40 J
Correct Answer: B
Solution :
Key Idea: Energy remains conserved in the process according to first law of thermodynamics. If an amount of heat Q is given to a system, a part of it is used in increasing the internal energy \[(\Delta U)\] of the system and the rest in doing work (W) by the system. Hence, we have \[Q=\Delta \,U+W\] (first law of thermodynamics) Given, \[Q=-30\,J,\,W=-10\,J\] \[\therefore \] \[\Delta U=-30+10=-20\,J\] \[\Rightarrow \] \[{{U}_{f}}=-{{U}_{i}}=-20\,J\] \[\Rightarrow \] \[{{U}_{f}}-40=-20\] \[\Rightarrow \] \[{{U}_{f}}=40-20=20\,J\]You need to login to perform this action.
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