Question

The pressure-volume diagram of a system undergoing thermodynamic transformation is shown in figure. The work done on the system in going from $A\to B\to C$ is $50J$ and $20cal$ heat is given to the system. The change in internal energy between $A$ and $C$ is

• A. $34J$
• B. $70J$
• C. $84J$
• D. $134J$

Answer 1

Answer: (A)

$34J$

Work done in a thermodynamic process= area under P-V diagram of the process
Given work done=$\Delta W(A\to B\to C)=50J$
Also heat given =$\Delta Q=20cal=84J$
From first law, change in internal energy= $\Delta U=\Delta Q-\Delta W=84-50=34J$