Question

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

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

Answer 1

The correct option is D 134 J

We know that 1cal=4.2J
Thus, heat absorbed=$\Delta Q=20cal=84J$,
work done by the system=$\Delta W=-50J$
From first law, change in internal energy $\Delta U=\Delta Q-\Delta W$
$\Rightarrow \Delta U=84+50=134J$