All Questions
18
questions
0
votes
1
answer
34
views
Does passing an electric current along a strip of metal submerged in saltwater cause anything?
If saltwater corrodes metal.
Can we effectively stop this by passing some electric current?
Has this been tried before?
4
votes
2
answers
235
views
Phenomological vs empirical
"Thermodynamics is a phenomenological theory"
I am not able to understand the difference between empirical and phenomenological descriptions, aren't all theories empirical?? Do we say some ...
- 592
0
votes
1
answer
206
views
What do these straight lines in the graph mean?
Does it mean thermal equilibrium? If the answer is yes, then how do we get to the molecular dissociation stage when we have already reached thermal equilibrium in vibrational mode?
Because equilibrium ...
- 47
9
votes
2
answers
1k
views
Does quantum mechanics halve the dimension of phase space?
In classical mechanics, a particle confined to move along only the $x$-direction can be fully described by a 2-tuple $(x_1,p_1)$ in phase space. In this case, the phase-space is clearly 2-dimensional. ...
- 1,581
1
vote
1
answer
87
views
What Are Some Examples of Physics Problems With Many Different Approaches That Give the Same Answer? [closed]
I was watching a clip of a lecture by Richard Feynman (see here), in which he states,
Every theoretical physicist whose any good knows six or seven different theoretical representations for exactly ...
- 307
4
votes
2
answers
409
views
How to fully understand the Definition of Entropy?
In the context of Thermodynamics and Statistical Mechanics we encounter, basically, three different definition of entropy:
First definition:
Consider an isolated macroscopic system, it has a ...
- 4,577
0
votes
0
answers
98
views
How did Planck integrate this?
How did Max Planck integrate this
$$\frac{dS}{dU}=\frac{1}{\nu} f\left(\frac{U}{\nu}\right)$$
in his paper "On the Law of Distribution of Energy in the Normal Spectrum" (equation 10) ?
5
votes
1
answer
762
views
Origin of conjugate variables in physical theories
Why do conjugate variables come in pairs? For example, in classical mechanics we have the generalized coordinates of position and momentum, and there is Jacobi's action-angle coordinates. Also, in the ...
- 2,749
1
vote
1
answer
284
views
Why is fresh asphalt dark
I have read that it is a mixture of bitumen and aggregate, stones and fillings.
But it does not explain why it get darker with time, is it the water so when it gets drier, it gets brighter? Or is ot ...
- 29k
1
vote
2
answers
315
views
Can a closed system be a non-equilibrium system?
Can a system without any interaction with other system be a non-equilibrium system; or is it that gain and loss is always needed for non-equilibrium?
- 595
1
vote
0
answers
237
views
How could I understand the concept of topological phase transitions?
I'm a freshman and don't have much knowledge about condensed matter theory, but I'm really interested in the concept of topological phase transitions; could someone explain it in a popular way?
1
vote
1
answer
458
views
canonical ensemble that is quantum mechanical and continuous?
I do not understand what the following statements from Wikipedia mean
For a canonical ensemble that is quantum mechanical and continuous, the canonical partition function is defined as
$$ Z = \...
- 2,107
11
votes
1
answer
1k
views
7/2 versus 9/2 for diatomic heat capacity
Question
I calculated the classical heat capacity of a diatomic gas as $C_V = (9/2)Nk_B$, however the accepted value is $C_V = (7/2)Nk_B$.
I assumed the classical Hamiltonian of two identical atoms ...
- 2,107
2
votes
1
answer
1k
views
Preventing Heat Escape
Is is possible to completely prevent heat from escaping from a closed container? Here is a diagram of vacuum flask, which tries to implement the design -
Vacuum Flask prevents heat from escaping in ...
- 23
5
votes
2
answers
3k
views
What's the true reason behind thermal expansion?
Thermal expansion is a normal concept everyday. There are 2 explanations:
1, thermal expansion result in stress, then result in deformation
2, thermal expansion result in deformation, then result in ...
- 115