Is a reversible isothermal process truly without energy change?

[chukie]

Hi!
I was just wondering if in a reversible isothermal process, there is a change in internal energy.
I know that for the isothermal forward process the temperature is constant so internal energy is constant? What really stumps me is the word reversible.

 

[Mapes]

In general, yes, the internal energy can change in a reversible isothermal process. (An exception exists for the case of an ideal gas, whose internal energy is a function of temperature only.)

 

[Moetasim]

Hello! You have brought up a very interesting topic. In a reversible isothermal process, the internal energy does not change. This is because the temperature is kept constant throughout the process, as you mentioned. However, the term "reversible" refers to the fact that the process can be reversed without any loss of energy or change in the system. Essentially, the system can go back to its original state without any net change in energy. This is due to the fact that the process is carried out in small, incremental steps, allowing the system to reach equilibrium at each step. In contrast, an irreversible process involves a net change in energy or a loss of energy due to the process being carried out in larger, non-equilibrium steps. I hope this helps clarify the concept of a reversible isothermal process.