What is the Entropy of a System with Doubly Degenerate Energy Level?

[Philip Wood]

An old book I have on elementary Statistical Mechanics (Rushbrooke) uses as an especially simple case a system with one energy level. This level is doubly degenerate. The author doesn't give an example of such a system. Can anyone think of one? And would it have entropy $k\ ln 2$?

[My thoughts turn to spin 1/2 particles but I'd like comment.]

 

[Dr. Courtney]

Real systems tend to have more than two energy levels, but some are approximated as two level systems in certain situations.

 

[TeethWhitener]

My thoughts turn to spin 1/2 particles but I'd like comment.

Yes, a spin 1/2 particle has a doubly degenerate energy level in the absence of a magnetic field.

 

[Philip Wood]

DrC and TW. Many thanks for replying.

TW: would you, then, say that a spin 1/2 particle, viewed as a system, has an entropy of $k\ ln2$ in the absence of a magnetic field?

 

[TeethWhitener]

TW: would you, then, say that a spin 1/2 particle, viewed as a system, has an entropy of k ln2 in the absence of a magnetic field?

Yes.