Entropy - Physical Meaning

  • Thread starter TimNguyen
  • Start date
80
0

Main Question or Discussion Point

Hello.

I know that entropy equals the Boltzmann's constant times the natural log of the multiplicity but I do not know the physical interpretation of what "entropy" really is. I understand the units of it are "Joules per Kelvin" but what does that really mean?
 

Answers and Replies

416
0
TimNguyen said:
Hello.

I know that entropy equals the Boltzmann's constant times the natural log of the multiplicity but I do not know the physical interpretation of what "entropy" really is. I understand the units of it are "Joules per Kelvin" but what does that really mean?
The most simple and direct interpretation

[tex]U = TS[/tex]

entropy is a "measure" of the increase of internal energy with temperature or

[tex]S = \frac{U}{T}[/tex]

If two bodies have the same temperature but one has more energy, then it has more entropy.

If two bodies have the same energy but one has less temperature, then it has more entropy.
 
Last edited:
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
Insights Author
2018 Award
35,222
4,039
TimNguyen said:
Hello.

I know that entropy equals the Boltzmann's constant times the natural log of the multiplicity but I do not know the physical interpretation of what "entropy" really is. I understand the units of it are "Joules per Kelvin" but what does that really mean?
Try this:

http://www.entropysite.com/

It has a good collection of basic articles, especially in dispelling the notion that entropy is nothing more than "disorder".

Zz.
 
416
0
ZapperZ said:
Try this:

http://www.entropysite.com/

It has a good collection of basic articles, especially in dispelling the notion that entropy is nothing more than "disorder".

Zz.
Nice link!

Effectively, the old (archaic) idea of entropy like disorder is not justified and would be abandoned of literature.

Moreover, the standard formula [tex]S = k \ ln W[/tex] often invoked in that old interpretation is valid only in the very special case of an isolated system at equilibrium.

That is reason that one would reasoning what is entropy from above formulas.
 
Hello.

I know that entropy equals the Boltzmann's constant times the natural log of the multiplicity but I do not know the physical interpretation of what "entropy" really is. I understand the units of it are "Joules per Kelvin" but what does that really mean?
ans:
it realy means how quickly the energy is spreding in medium.
 

Related Threads for: Entropy - Physical Meaning

Replies
1
Views
770
  • Last Post
Replies
2
Views
788
Replies
1
Views
1K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
12
Views
1K
Replies
1
Views
2K
  • Last Post
Replies
4
Views
658
  • Last Post
Replies
5
Views
742
Top