The $p-V$ diagram of a system undergoing thermodynamic changes is as shown in the figure. The work done by…
The $p-V$ diagram of a system undergoing thermodynamic changes is as shown in the figure. The work done by the system in going from $A \rightarrow B \rightarrow C$ is $30 \mathrm{~J}$. If $68 \mathrm{~J}$ of heat is given to the system, then the change in the internal energy of the system between $\mathrm{A}$ and $\mathrm{C}$ is
$34 \mathrm{~J}$
$55 \mathrm{~J}$
$55 \mathrm{~J}$
$38 \mathrm{~J}$
Solution
We know that heat absorbed $=\Delta Q=68 \mathrm{~J}$,
Work done by the system $=\Delta W=30 \mathrm{~J}$
From the first law of thermodynamics, the change in internal energy is given by,
$\begin{aligned} & \Delta U=\Delta Q-\Delta W \\ & \Rightarrow \Delta U=68-30=38 \mathrm{~J}\end{aligned}$
