Seebeck and Peltier

Discussion in 'General Electronics Chat' started by Rolland B. Heiss, Mar 19, 2015.

  1. Rolland B. Heiss

    Thread Starter Member

    Feb 4, 2015
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    Lately I've been quite interested in the Seebeck effect as well as the Peltier discovery. I haven't had much time to experiment lately what with work and my scrapping and recycling old component activities. Also I have three CRT TV sets that I know I can fix once I get around to diagnosing the minor problems with them. But anyway, I did try an experiment two days ago in which I used a stainless steel rod taken from an old non working printer and hooked up some very decent solid copper wire pulled from a TV that was trashed beyond repair to that rod. Outside, after I placed part of the stainless steel rod into the ground about an inch or so into the earth I wrapped the copper wire to the top of the rod (and the sun was shining quite brightly that day which provided some decent heat) and then I straightened the copper wire all the way down to the grass. Now I didn't just leave it as two equal lengths in relation to the copper wire and the steel. I had the copper much longer and wrapped it around where it sat on the ground about 12 times in order to form a coil which merely sat upon the grass. This gave me a reading of about 300 millivolts. Interesting I thought. So I took the configuration inside and did the same thing (without the benefit of sticking the stainless steel rod into the earth but merely connected it to the ground metal on my desk) and then lit a tea candle and heated the area where the copper and steel connected. After waiting a very long time I only got about .8 millivolts doing that. I figured the results would be lower but I didn't expect that large a drop in potential. When I blew on it or waved an envelope over it I got .9 millivolts inside for a brief moment but that's it. Why the terribly poor performance indoors and the incredibly better (albeit also poor relatively speaking) performance outside? After all, inside I had direct heat on the copper and stainless connections! I thought it might (maybe) do better but the indoor results were terrible. So I'll ask the question as a child would. How come??? :confused:
     
    Last edited: Mar 19, 2015
  2. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    Temperature gradient with the Seebeck effect. The voltage is caused by charge separation. Electrons move randomly faster on the heated side from thermal energy causing a small charge imbalance with the slower electrons on the colder side. The electrons on the hot side then move to neutralize the total charge of the conductor creating an electric field across it. If the rod was mainly uniformly hot across a large surface there's little or no imbalance to create the electric field.
     
  3. Rolland B. Heiss

    Thread Starter Member

    Feb 4, 2015
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    Thanks for the informative response Spook. Very much appreciated!
     
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