Understanding the Mechanics of Galileo Temperature Gauges

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Discussion Overview

The discussion centers on the mechanics of Galileo temperature gauges, exploring how they function based on principles of density and buoyancy. Participants inquire about the behavior of the glass bubbles in relation to temperature changes and the materials involved in their construction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions why the bubbles fall when the liquid becomes less dense, suggesting that increased volume compresses the air in the bubbles, affecting buoyancy.
  • Another participant asks whether the different sizes of the bubbles indicate they are filled with different liquids or if they have different weights with the same liquid.
  • A participant expresses confusion about the relationship between density and weight, questioning how a decrease in density could lead to an increase in weight.
  • In response, another participant clarifies that it is the supporting liquid's density that changes, not the bubbles themselves, and explains that the bubbles are designed to have specific densities that correspond to the temperature of the supporting liquid.

Areas of Agreement / Disagreement

Participants exhibit some confusion and differing understandings regarding the mechanics of density and buoyancy in the context of the thermometer's operation. There is no consensus reached on all points, as some questions remain open for further exploration.

Contextual Notes

Some participants express uncertainty about basic principles of density and buoyancy, indicating a need for further clarification on these concepts. The discussion does not resolve all misunderstandings or assumptions regarding the mechanics of the thermometer.

Lrdmora
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Okay, this is not for homework, just curious. I was at a friends this weekend and he had a Galileo temperature gauge. I was trying to figure it out.

It is full of glass bubbles that are half full of liquid, some small, some large, with glass weights at the bottom and markers.

As the temperature rises the liquid in the oval bubbles becomes less dense.

Heres my first question: If the liquid becomes less dense what causes it to fall? My belief from placing it near the fire place and watching it, is that as the volume of the liquid increases it compresses the air or gas in the bubble making it less buoyant. (The liquid actually rises to above the halfway mark when hot) Will someone set me on the correct path?

My second question: I noticed that the bubbles were different sizes. And that they fall at different temperatures. Are the bubbles filled with different liquids that react at different temperatures, or are the weights of the bubbles different with the same liquid.

I know this is an elementary question, but I sure would appreciate any answers to appease my curiousity.

Thanks a ton.
 
Science news on Phys.org
http://www.hewgill.com/galilean-thermometer/

- Warren
 
Last edited by a moderator:
I guess I am missing a basic thing.

Thanks for the link! But I am slow today.

How does the density of the object decreasing make it weigh more? I thought increasing the density would make it heavier? What am I missing?
 
I think you've misunderstood. It is not the liquid in the "bubbles" that becomes more or less dense, it is the liquid that is supporting them.
The "bubbles" themselves are rigid. There volume does not change, of course, the mass does not change, so the overall density remains the same (the density of the gas or liquid inside each "bubble" is irrelevant- since the overall volume does not change, neither does the overall density.
The "bubbles" are made with more or less glass so that the density of each one is the same as density of the supporting liquid at some specific temperature. When the liquid reaches a given temperature, all "bubbles" with density greater than that of the liquid at that temperature sink.
 
Thank you!

That makes a lot more sense! I guess I was being a little dense myself, heh, heh.

Thanks for taking the time to explain something elementary to me.
 

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