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3 votes
1 answer
64 views

Total differential of internal energy $U$ in terms of $p$ and $T$ using first law of thermodynamics in Fermi's Thermodynamics

While reading pages 19-20 of Enrico Fermi's classic introductory text on Thermodynamics, I ran into two sources of confusion with his application of the First Law. Fermi introduces a peculiar notation ...
user104761's user avatar
-1 votes
3 answers
86 views

Proof that small change in temperature leads to small change in entropy

I have been trying to find a mathematical proof (or even from a reliable source) which verifies that/proves that: A small change in temperature leads to a small change in entropy. However, I was ...
PhysicsLover's user avatar
1 vote
1 answer
62 views

Weird derivative with respect to inverse temperature identity in Tong's statistical physics lecture notes

While reading David Tong's Statistical Physics lecture notes (https://www.damtp.cam.ac.uk/user/tong/statphys.html) I came across this weird identity in page 26 (at the end of the 1.3.4 free energy ...
duodenum's user avatar
1 vote
1 answer
463 views

Currently self-studying QFT and The Standard Model by Schwartz and I'm stuck at equation 1.5 in Part 1 regarding black-body radiation

So basically the equation is basically a derivation of Planck's radiation law and I can't somehow find any resources as to how he derived it by adding a derivative inside. Planck says that each mode ...
Megat Nurul Anwar's user avatar
2 votes
0 answers
83 views

Is my geometric interpretation of $T \left(\frac{\partial S}{\partial T}\right)_P = \left(\frac{\delta Q}{dT}\right)_P$ correct?

I originally started writing this as just a question, but in the process of writing it I may have solved it myself. Still, I would very much appreciate if someone more knowledgeable than myself took a ...
ummg's user avatar
  • 1,215
2 votes
3 answers
152 views

Temperature and entropy

One could define temperature as follows: $$T^{-1} = \left(\frac{\partial S}{\partial U}\right)_{N,V}$$ I was reading Schröder, and he says that we can define temperature in another way: $$T = \left(\...
Not's user avatar
  • 23
0 votes
0 answers
281 views

Partial derivatives in thermodynamics

In thermodynamics many definition has been made from partial derivatives at constant conditions for instance: Let U be U:$f(S,V,m_k)$ then: $$T = \left( \frac{\partial U}{\partial S} \right)_{V, m_{...
Ilya_Curie's user avatar
0 votes
2 answers
282 views

Regarding directional derivatives [closed]

we know directional derivatives are the rate of change of any given scalar field along the given direction, and it is also equal to scalar product of gradient of the field and the unit vector along ...
jai ho's user avatar
  • 13
1 vote
1 answer
5k views

What's the meaning for the derivatives for temperature and pressure?

If we view the temperature and pressure as the function of time and space, $$T = T(x,y,z,t) \quad ; \quad P = P(x,y,z,t)$$ then what's the meaning for the following derivatives? $$\nabla T \...
Jack's user avatar
  • 1,757
7 votes
6 answers
8k views

How is gradient the maximum rate of change of a function?

Recently I read a book which described about gradient. It says $${\rm d}T~=~ \nabla T \cdot {\rm d}{\bf r},$$ and suddenly they concluded that $\nabla T$ is the maximum rate of change of $f(T)$ ...
Inquisitive's user avatar