Reversible expansion of an ideal gas under isothermal and adiabatic conditions are as shown in the figure (AB Isothermal, AC Adiabatic). Which of the following options is not correct?

ShutterstockLet's analyze the options for expansion:$AB$ is Isothermal: $T_A=T_B$. (Correct)In expansion, the work done is the area under the curve. The isothermal curve lies above the adiabatic curve, so $W_{\text{isothermal}}>W_{\text{adiabatic}}$. (Correct)$\Delta S_{\text{adiabatic}}=0$ (for reversible process), while $\Delta S_{\text{isothermal}}>0$. (Correct)In adiabatic expansion, the gas does work at the expense of its internal energy, so the temperature decreases ($T_C<T_A$). Thus, $T_C>T_A$ is incorrect.