A) 18 J
B) 9 J
C) 4.5 J
D) 36 J
Correct Answer: A
Solution :
Key Idea: Energy remains conserved in the process according to first law of thermodynamics. When an amount of heat Q is given to a system, a part of it will be used in increasing the internal energy \[(\Delta U)\] of the system and the rest in doing work (W) by the system, hence \[Q=\Delta U+W\] Heat released by system \[Q=-20\,J\] Work done on the gas \[W=-8\,J\] \[\therefore \] \[\Delta U=Q-W\] \[=-20-(-8)\] \[=-12\,J\] Final internal energy \[{{U}_{f}}={{U}_{i}}+\Delta U=30-12=18\,J\].You need to login to perform this action.
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