Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Questionable interpretation of physics

I wrote:

>>You can't write TdS as dQ

Carl Mungan wrote:

True in general. But it's okay for the special case of a reversible

Actually you don't even need a "reversible" path.
Any path will do -- any fixed, simply-connected path.

A path of constant T will do, and is often useful.
A path of constant T+S will do, but is not very often
useful or physically significant.

You just integrate TdS along such a path, call the result
the Q du jour, and differentiate it to get dQ.

-- You need to specify *which* path, either by decorating
Q with subscripts, or perhaps by reeeally explicit context.
-- You cannot extend this type of Q-on-a-path to cover the
(T,S) plane, or any nontrivial subset thereof, or any other
nontrivial more-than-one-dimensional region ... because
the Qs for different paths will be mutally incompatible.
Do not imagine that there is any potential of the form
Qreversible(T,S) any more than there is a Q(T,S).
For details including pictures, see
and references therein.