In TD one can write dU=TdS while V and N do not change.
This sounds like adding a little bit of entropy "dS" in the system to increase the internal energy by "dU" but how would a smart person actually add a little entropy "dS" into anything?

Question

In TD one can write dU=TdS while V and N do not change.
This sounds like adding a little bit of entropy "dS" in the system to increase the internal energy by "dU" but how would a smart person actually add a little entropy "dS" into anything?

anonymous · Answer

Just like the equation suggests, you can increase the entropy by adding a little bit of heat (changing the internal energy) but WITHOUT changing the temperature.

In other words, increase dU while keeping T constant... and you have effectively increased the entropy :)