AVR-Chat

The liquid in the modern version of Galileo's Thermoscope may not be
water... As I understand it, in the original version the floats were open,
inverted 'cups' in which the trapped air changed volume with temperature,
causing the floats to rise or fall. The modern version uses sealed floats
and a supporting fluid that changes density with temperature.

Besides, the question is how to measure the depth of a water tank, not its
temperature. The incompressibility of water makes density changes with depth
extremely small. The same doesn't hold true for its coefficient of thermal
expansion.

-----------------------------------
Bob Tilden, tilden@northwestern.edu
High Energy Physics Group
Northwestern University


-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Jim Wagner
Sent: Friday, May 15, 2009 9:59 AM
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Re: water level meter

This is exactly why the floaters in a Galilleo's Thermoscope hover at  
a specific depth. There is a density gradient in a column of fluid. At  
a greater depth, the floater is lighter than the fluid it displaces  
and at a lesser depth, it is heaver than the fluid it displaces.  
Definitely a second order effect, but still important.

Jim Wagner

On May 15, 2009, at 4:58 AM, Brian wrote:

>
>
> I was on Submarines in the Navy. They do compress but that is under  
> a couple hundred feet of water. the compression of the plastic ball,  
> could even be solid, should be small and still produce a measurable  
> upforce with depth.
>
> Brian
> --- In AVR-Chat@yahoogroups.com, David VanHorn <microbrix@...> wrote:
> >
> > On Thu, May 14, 2009 at 11:37 PM, dlc <dlc@...> wrote:
> > > Ahem,
> > >
> > >   Water density is a constant, water _pressure_ increases with  
> depth,
> > > and if the ball acts the way my BC does, the air in the plastic  
> ball
> > > loses buoyancy as the water depth increases.  But since my BC  
> compresses
> > > with depth and the plastic ball probably wouldn't, that might  
> not be so.
> > >  These are basics every diver learns.
> >
> > So the effect is smaller, and the slope runs the other way, but it  
> still works.
> > :)
> >
> > Submarines compress, I imagine a plastic ball will too.
> >
> >
> > --
> > There is no computer problem which cannot be solved by proper
> > application of a sufficiently large hammer.
> >
>
>
> 



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