Thermoelectric education

Submitted by pa.conroy on Sat, 2010-08-21 09:44
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 I am seeking a simple demonstration of the Peltier effect for use in the classroom.


The material I have found is not explicit enough and I have not been able to make the circuits workto demonstrate the effect. For example, where do I get aluminum wire or iron wire and should the junctions be soldered?  Does anyone have a suggestion as to a source of a simple demonstration?


My latest version uses a 9V battery, 1kO resister, galvenized steel wire (for picture hanging). The circuit is cathode, resistor, Fe, Cu, Fe, anode but there is no temperature effect at either junction.


 

Submitted by cvining on Mon, 2010-08-23 19:09

Here is a good web-link for a thermoelectric science fair project, which could also be the basis for a good classroom demonstration:

 

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p055.shtml

 

That article also cites this paper:

 

Winder, E.J., et al. "Thermoelectric Devices: Solid-State Refrigerators and Electrical Generators in the Classroom." Journal of Chemical Education, Vol. 73, No. 10, p. 946. Retrieved August 23, 2010.

 

Those two links should get you off in the right direction.

 

The trouble with using simple metal wires like Fe or Cu (or Al), as you've discovered, is that the effect is rather small and difficult to observe.  You would have to be very careful about unintended resistances at the joints and other bad effects, just to observe anything at all.  Even solder joints have some resistance.

 

These commercial modules are built using semiconductors with much, much larger thermoelectric response than those wires.  You should be able to observe cooling even using a simple battery for power.  With a little practice, you should be able to freeze water without much trouble.  That makes a rather vivid demo.

 

BTW, you can get working TE modules off of e-Bay at a very good price.

 

Best of luck!