Two gases have the same initial pressure P, volume V and temperature T. They both expand to the same volume from V to 2V, one adiabatically and the other isothermally. Plot P-V diagram for the given situation and hence explain. In which case is the final temperature greater?

Explanation

Figure shows the P-V diagrams for two gases expanded from volume V to 2V. As an adiabatic is steeper than an isotherm, so the adiabatic expansion curve AB lies below the isothermal expansion curve AC.

`P_B` and `P_C`are the final pressures for adiabatic and isothermal expansions respectively. Clearly,`P_C gt P_B`. Hence the final pressure is greater for the isothermal expansion.