Re: W+Q deprecated

[Jim Green <JMGreen@SISNA.COM>]

> >  >Okay. I've got a gas of magnetic atoms. I slowly change the current
> >>which flows both through a set of Helmholtz coils around the gas and
> >>an electrical heater immersed in the gas.
> >
> >Is the deltaE due to Q or W? How would you know?
> >
> >Is deltaS=Q/T?   How would you know?
>
> Would you agree that it takes work W (exertion of a torque over an
> angle) to flip a group of spins in an organized manner by the coils?
> This doesn't look like heat to me. The fact that the flipping is done
> coherently is the key idea that entropy isn't changed.

Yes, work is done, but I still don't know whether to call that work W or Q
-- If it is W then S doesn't change -- If Q, then it does.   If both
change, then we are back at the place of saying the TFL is useless

(BTW there is no such thing as "heat" to look at.  Physics communications
should be precise.  I don't have a constant physics meaning for the word
"heat." I doubt if anyone does.)

Can you calculate dS for the process you describe?

The only process where I can calculate dS meaningfully (for dS=Q/T) is the
standard adiabatic cylinder.  So that is the only situation where dE=Q+W is
meaningful.  Therefore, the Law is essentially useless.  TFL is an
historical fluke.  This is the position I have taken here for over 10
yr.  And happily is a position where John and I agree.

Jim


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen