Re: [Phys-l] Temp & Energy density

["Paul Lulai" <plulai@stanthony.k12.mn.us>]

Thanks John.

If this results in an increased P wouldn't the accompanying decrease  
in V (since the piston snuck down a bit when none of the gas particles  
were looking) result in an increased T?  Or is this using pv=nrt when  
it doesn't apply?
A material science prof and a physicist (both working separately on  
low pressure environments: 1 on material characterization the other on  
thin film deposition) both teased me with the piston question.  I  
don't know if they were on cahoots or not.
My response was no temp change due to no real work. They seemed (at  
the time) to find this acceptable. I've just been approached with the  
energy density arguement. I'm trying to resolve the two conceptions.

I appreciate the help. Thanks fir your responses and patience.

Sent from my iPod so I can blame Apple for my typos.

Paul Lulai
St. Anthony Village Senior High
Http://prettygoodphysics.wikispaces.com
US First RoboHuskie Team 2574


On Aug 3, 2009, at 11:18 PM, "John Mallinckrodt" <ajm@csupomona.edu>  
wrote:

> Paul Lulai wrote:
>
> > Larger energy density implies increase in temp.
>
> Simply not so.  Others seem not to have directly addressed the
> central misconception here so allow me.
>
> Example:  For a monatomic ideal gas at equilibrium
>
>     PV = Nkt = (2/3)U
>
> thus
>
>     energy density = U/V = (3/2)P
>
> That is, energy density is directly proportional to equilibrium
> pressure and has no direct connection to temperature.
>
> John Mallinckrodt
> Cal Poly Pomona
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