## Irreversible and Reversible Expansion

Boltzmann Equation for Entropy: $S = k_{B} \ln W$

Bianca Barcelo 4I
Posts: 74
Joined: Fri Sep 28, 2018 12:17 am
Been upvoted: 1 time

### Irreversible and Reversible Expansion

How does irreversible and reversible expansion work? What is happening conceptually with the gas and when is pressure constant?

Emmaraf 1K
Posts: 94
Joined: Sat Oct 20, 2018 12:16 am

### Re: Irreversible and Reversible Expansion

In irreversible expansion, the outer pressure will suddenly drop from say 2 to 1 ATM and so the piston will constantly be pushing against 1 ATM of pressure. In reversible expansion, the pressure outside slowly drops bit by bit from 2 to 1.9 to 1.8 to 1.7 (not actually by .1 but by an infitesimally small amount) so the piston is pressing against a little bit less pressure each time. The reversible expansion does more work because it doesn't press by 1 ATM constantly but by 1.9 to 1.8 to 1.7 (again not exact values) and so on and so forth.

Patrick Cai 1L
Posts: 93
Joined: Fri Sep 28, 2018 12:25 am

### Re: Irreversible and Reversible Expansion

Reversible can be thought of as if the system and surroundings are at equilibrium, where any change in volume can be seen as a infinitesimally close to the original thermodynamic state; irreversible tends towards one direction and no small change can restore initial conditions.

Return to “Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy”

### Who is online

Users browsing this forum: No registered users and 1 guest