Re: Entropy and dQ vs dW

On Jul 30, 7:36 am, Uncle Ben <b...@xxxxxxxxxxx> wrote:
On Jul 29, 4:44 pm, jbriggs444 <jbriggs...@xxxxxxxxx> wrote:





On Jul 29, 1:24 pm, Uncle Ben <b...@xxxxxxxxxxx> wrote:

On Jul 29, 7:16 am, jbriggs444 wrote

.....
The hand that rubs the block does no work on the block.
The block that is rubbed by the hand does negative work on the hand..

How kind of you to straighten out us poor mortals!

But, sir, if no work is done on the block, why does it get hot?

Not my problem, bub.  I'm educating you about kinematics.  The work
done _is_ zero.

To oversimplify a fair bit, kinematics is about the transfer of
kinetic energy.  You're talking about the generation of heat.  Two
different things.

And there was this American with a European title -- Count Rumford, I
believe -- who made cannons for the Austrian army.  He tried boring a
cannon with a dull drill, for scientific purposes, and found that the
cannon would get hot enough to boil water.  He kept going and boiled
yet more water. He said he thought he could keep boiling water long
after any phlogiston had gone away.

So he told the world that work was a form of energy like heat and we
got the First Law of Thermodynamics.

And what was the definition of "work" that he used?

Now there was a rigid body being rubbed by a large metal finger.
Where did all that energy come from if no work was being done on it?

Kinetic energy is being removed from the finger.  Why should it not
show up as heat?

Heat and work are technical terms in thermo0dynamics.  Heat is energy
transferred because of  a difference in temperature. (None in the
present example.)  Work is every other form of energy transfer;  in
this case, force times distance.

Look up Rumford and the first law of thermdynamics. Kinetic energy is
not the only possible result of work done.

-- Bub!

Uncle Ben- Hide quoted text -

- Show quoted text -

I find it amusing that Mr. Briggs wants to educate me about
thermodynamics, but he has to ask me for the definitions of heat and
work. :-)

Uncle Ben
.

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