question_answer

When a system is taken a from state i to state f along the path iaf, it is found that  \[Q=50\]cal and \[W=20cal.\], Along the path ibf \[Q=36\]cal. W along the path ibf is

A) 14 cal

B) 6 cal

C) 16 cal

D) 66 cal

Correct Answer: B

Solution :

[b] For path iaf, \[Q=50cal~~W=20cal\] By first law of thermodynamics, \[\Delta U=Q-W\text{ }=50-20=30cal.\] For path ibf        \[Q'=36cal\] \[W=?\]     or, \[W=Q'-\Delta U'\]   Since, the change in internal energy does not depend on the path, therefore \[\Delta U'=30cal\] \[\therefore W=Q'-\Delta U'=36-30=6cal.\]