A gas is expanded from volume ${\mathrm{V}}_0 = \mathrm{to} 2{\mathrm{V}}_0$ under three different processes. Process 1 is isobaric process, process 2 is isothermal and process 3 is adiabatic. Let $∆{\mathrm{U}}_1, ∆{\mathrm{U}}_2 \mathrm{and} ∆{\mathrm{U}}_3$ be ihe change in internal energy of the gas in these three processes. Then:

 

Process 2 is an isothermal process. Hence, $∆{\mathrm{U}}_2 = 0$.
Process I is an isobathic (P = constant) expansion.
Hence, temperature of the gas will increases;
or $∆{\mathrm{U}}_1$ = positive
Process 3 is an adiabatic expansion. Hence, temperature will decrease;
or $∆{\mathrm{U}}_3 =$negative
Therefore, $∆{\mathrm{U}}_1>∆{\mathrm{U}}_2>∆{\mathrm{U}}_3$ is the correct option.