Now let us apply the above results to evaluate the entropy of the universe when a system interacts with the surroundings. Refer to Figure 23.2.
![](images/23.2.gif)
Figure 23.2
Let Temperature of the surroundings ![](images/image030.gif) Temperature of the system ![](images/image032.gif)
and,
![](images/image034.gif) |
(23.7) |
If the energy exchange takes place, will be the energy transfer from the surroundings to the system.
![](images/image038.gif) |
(23.8) |
![](images/image040.gif) |
(23.9) |
![](images/image042.gif) |
(23.10) |
[since ] |
(23.11) |
So,
![](images/image048.gif) |
(23.12) |
If the system is isolated, that is, when there is no interaction between the system and the surroundings, then
![](images/image050.gif) |
(23.13) |
|