I didn't take notice of the original post which gave rise to these quotes
so I don't know whom I am quoting. At least in part I think that it is
Ludwik.
|>..........................................................................
|>The energy related threads made me aware that thermodynamic heating
|>(a process by which the internal energy of a system is changed due to a
|>difference of temperatures between the inside and outside) should not be
|>confused with "pseudo-heating", for example, when a penetrating radiation
|>(alpha particles, electrons, photons, etc.) is entering a system or when
|>a chemical reaction is taking place inside (a barrier separating reactants
|>is removed, frictionlessly).
|>
|>Any temperature changing processe, OTHER THAN HEATING, should be called
|>working. Common mechanical working (applying a force to a moving particle
|>Sending an electric current through a resistor should be called workig
|>and not heating. Cooking in a microwave oven is predominately working;
|>a meal would be ready sooner if heating could be eliminated. Saying that
|>a fillament is "heated electrically" is bad physics. It was OK before but
|>it is not OK now. I am not trying to be sorcastic. This is logical and
|>our vocabulary must be modified. Would you agree? How can this be done?
|>
|>Note that one can also argue, as Jim does,
|> http://www.sisna.com/users/jmgreen/first.html
This is an old URL -- After SISNA and then I have fiddled with things the
current one is as follows:
As to the meaning of heating and work (I make it a practice not to use evil
four letter words) let me add the following:
The only distinguishing characteristic between heating (an action) and
work (an action) is that heating changes the entropy and work does not.
Thus a system sitting on a hot plate, being played on by a propane torch,
having an internal resistor energized by a battery (internal or external
-- it doesn't matter), being bombarded by high energy particles/photons,
being in a microwave oven, all are HEATING because they all (I think)
change the entropy. A moving piston compressing a gas does NOT change the
entropy and therefore does WORK. (The proof of this is not yet on the WWW
page -- I will put it there if there is sufficient interest.)
BUT the Second Law must remain intact after all the verbiage: DS=Int(DQ/T)
-- if an action changes the entropy, the action is heating -- and this has
little to do with "hot" things. And there need not be an obvious
difference in temperature to do "heating". Q is not a substance anymore
than W is. They are _actions_.
It should be quite legitimate to say "filament heated by an electric current"
|>that the process of increasing a temperature by placing a cup on a hot
|>plate is also working. Why? Because this is done through collisions
|>of atoms and molecules. Are we ready to say that heating does not
|>exist (as an acceptable word in teaching physics)?
|>
Ludwik, HEATING surely exists, it is "heat" (ugh I contaminated myself)
which does not exist. Just remember to say "do work" and "do heating", but
NEVER use the evil four letter word as a noun.
I don't see a valid use for the term "pseudo- heating".
| We call this form of energy
|>HEAT ENERGY, but we know it is not really a new form, it is just
|>kinetic energy - internal motion."
Only if we want to mislead our students would we say something like this:
We have a perfectly good term already "Internal Energy" why confuse
ourselves and our students with anything different?
OK, I hope this does it for this year. (:-)
Please visit the FirstLaw WWW page and give me some feedback where
improvements can be helpful.