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$P-V$ diagram of a cyclic process $ABCA$ is as shown in figure. Choose the correct statement
$\Delta {Q_{A \to B}}$= negative
$\Delta {U_{B \to C}}$= positive
$\Delta {W_{CAB}}$= negative
All of these
Solution
(d) During process $A$ to $B$, pressure and volume both are decreasing.
Therefore, temperature and hence, internal energy of the gas will decrease ($T \propto PV$) or $\Delta {U_{A \to B}} = $negative.
Further $\Delta {W_{A \to B}}$ is also negative as the volume of the gas is decreasing. Thus $\Delta {Q_{A \to B}}$ is negative.
In process $B$ to $C$ pressure of the gas is constant while volume is increasing.
Hence temperature should increase or $\Delta {U_{B \to C}}$= positive.
During $C$ to $A$ volume is constant while pressure is increasing.
Therefore, temperature and hence, internal energy of the gas should increase or $\Delta {U_{C \to A}}$= positive.
During process $CAB$ volume of the gas is decreasing. Hence, work done by the gas is negative.
