Re: [Phys-l] T dS versus dQ

[Bernard Cleyet <bernardcleyet@redshift.com>]

To be more specific:

I wanted an easily constructed device wherein one may demonstrate the difference between entropic and isentropic addition of energy into a gas.  True, doing both mechanically would be better, but as I wrote, I think it's expensive to do that.  I just "now" thought, why not add energy very slowly via the heater and compare w/ rapidly, BUT that would make a very great demand on the insulation.  I suppose (from the advanced lab list) one could jacket the cylinder w/ a PID controlled heater to match the temp inside**.   

BTW anybody know the functional relationship of rate of compression w/ the rate of increase of S?    


** like a guard element in an electrical experiment or an accelerating cage in a direct measure of g.

bc


On 2010, Jan 18, , at 17:08, chuck britton wrote:

> At 4:47 PM -0800 1/18/10, Bernard Cleyet wrote:
> > I shoulda used "skeptical".   and added I hope they will be.
> >
> > RE: creating entropy.  I'm further confused.  I thought adding E via 
> > a heater would be entropic while adding E via P dV (slowly*) would 
> > be isentropic, with the end states being different for the same E.
>
>
> If I'm getting this right - the heater WOULD be just as 'entropic' as 
> the speaker is. The speaker is a closer analog of fast moving piston. 
> The 'mechanics' of the heater are way different. Speaker is still 
> 'mechanical'. I think that it is the similarity of the speaker to the 
> piston that is being stressed.
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