# Approach to Equilibrium

The Box Equilibrium model simulates a box that is divided into two parts of equal volume. The left half initially contains a gas of N identical particles and the right half is empty. We then make a small hole in the partition between the two halves. What happens? We expect that after some time, the system reaches equilibrium, and the average number of particles in each half of the box is N/2. The purpose of this simulation is to gain insight into the tendency of macroscopic systems to approach a well defined equilibrium macrostate and the importance of fluctuations in equilibrium.

## Reference:

Gould and Tobochnik Statistic and Thermal Physics p25 to be published by Princeton University Press (2010). Draft chapters are available online at <http://stp.clarku.edu/>.

### Note:

This simulation was created by Wolfgang Christian using the Easy Java Simulations (Ejs) modeling tool. It is based on a Java program from the Statistical and Thermal Physics Project. You can modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu. Information about Ejs is available at: <http://www.um.es/fem/Ejs/>.