## Example of reversible expansion?

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

Xinyi_Yan_3L
Posts: 21
Joined: Wed Sep 21, 2016 2:56 pm

### Example of reversible expansion?

For irreversible expansions, an example would be a piston with atmosphere as external environment. But can some one give me a real-life situation as an example of a reversible expansion, if there's any? I understand in reversible expansion process, the pressures of the system and exterior are always the same. It's just hard to exemplify.
Also, what does "reversible" actually mean? Does that literally mean the expanded volume can decrease to its original state?

Jingyuan_Fu_3E
Posts: 8
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Example of reversible expansion?

I feel that the reversible expansion is more or less an ideal situation with the same internal and external pressure. "Reversible" here is similar to the "reversible" characteristic of a chemical equilibrium, where the infinitesimall changes in reactants and products are always occurring but the system remains equilibrium. When the gas system remains equilibrium, the infinitesimall change in external or internal gas pressure would be big enough to cause expansion, which in reverse, shifts the system back to equilibrium. Not sure if it helps.