1. Are you getting tired of gases?
dU = TdS - pdV
dW = -pdV worked well for gases!!
However, in other physical systems, dW = xdX.
[x, X] conjugate variables
x: force (intensive variables)
X: displacement (extensive variables)
System x X dW
fluids -p V
-pdV
elastic rods
f (tension) L
fdL
liquid films
g (surface tension) A
gdA
dielectric materials
E (electric field) pe
Edpe
magnetic materials
H (magnetic field)
m= -MV
Hdm

2. Magneto X men

3. Adiabatic Demagnetization

4. Entropy exchanged between spins and phonons !

5. TdS equations (TediouS equations)
The TdS equations are useful for calculating :
heat transferred in reversible processes
entropy by dividing by temperature and then integrating
heat flow in terms of measurable properties
relationship between coordinates for isentropic processes