Sign in or 
- EasyEdit
- Edit tags
-
(what's this?What are these tools?
People just like you can add or edit the content on this site. If you want to try editing, but aren't ready to add to this site, try our demo area.
Read more about editing pages at Wetpaint Central.
) - Report page
Share this
Second main principle
In thermodynamics, the second main principle, in contrast to the first main principle, of the mechanical theory of heat is defined by the following two equivalent expressions: [1]
or
where dQ is an amount of heat imparted to a body, T is the temperature of the body at the point of heat transfer, and dS is the change in the transformation content of the body or of entropy change. These expressions were the formulations used by German physicist Rudolf Clausius, which he characterized as "convenient in the case of certain investigations", later coming to be known as the second law of thermodynamics. Clausius also called this the “principle of equivalence of transformations”, another formulation of what later came to emerge as the second law.
References
1. Clausius, Rudolf. (1879). The Mechanical Theory of Heat (pg. 90), London: Macmillan & Co.
2. ibid, Chapter IV: The Second Main Principle under another Form, or Principle of the Equivalence of Transformations (pgs. 91-109).
or
dQ = TdS
where dQ is an amount of heat imparted to a body, T is the temperature of the body at the point of heat transfer, and dS is the change in the transformation content of the body or of entropy change. These expressions were the formulations used by German physicist Rudolf Clausius, which he characterized as "convenient in the case of certain investigations", later coming to be known as the second law of thermodynamics. Clausius also called this the “principle of equivalence of transformations”, another formulation of what later came to emerge as the second law.
References
1. Clausius, Rudolf. (1879). The Mechanical Theory of Heat (pg. 90), London: Macmillan & Co.
2. ibid, Chapter IV: The Second Main Principle under another Form, or Principle of the Equivalence of Transformations (pgs. 91-109).
Sadi-Carnot |
Latest page update: made by Sadi-Carnot
, Apr 7 2009, 6:43 PM EDT
(about this update
About This Update
new
- Sadi-Carnot
172 words added 2 images added view changes - complete history) |
|
More Info: links to this page
|
| Started By | Thread Subject | Replies | Last Post | ||
|---|---|---|---|---|---|
| Perrot | Entropy, Second law | 2 | Sep 3 2009, 11:11 AM EDT by Sadi-Carnot | ||
|
Thread started: Apr 10 2009, 5:27 AM EDT
Watch
I do not agree with the above statement: The second law is NOT defined by the expression dS=dQ/T. Actually entropy must be defined. There is a THEOREM which states that "IF a transformation is reversible (which suppose that the word "reversible' has been defined beforehand), THEN dQ/T is a total differential". A rigorous proof of this theorem is not hard to find. In other words, it means that IF a transformation is reversible, THEN it exists a function whose differential is dQ/T. As this function exists, it is designed as "entropy" (a word coined by Clausius) and labelled S. As a consequence, the expression dS=(dQ/T)reversible is the relation of definition of the entropy. It is not the second law. The second law states that IF a transformation is irreversible, THEN dS=(dQ/T)+something else which must be positive. The concept of reversibility is important and must be well understood.
|
|||||
Showing 1 of 1 threads for this page
