Expert: Steve Johnson - 6/3/2009

Question
sorry sir  i am asking this question after asking what is seebeck effect.
i want to know that why does one junction of a different metal pairs becomes cold and antoher junction becomes hot on passsing currnet through the pair in a particular direction. can you explain it .
thanks
kats

Answer
Hello kats,

The Peltier effect is the compliment to the Seebeck effect. Explaining is very difficult. I found one site that does fairly well.
http://www.tellurex.com/12most.html#top
I will go back to the idea I invoked to explain the Seebeck effect -- about hot electrons making better progress through the conductor than cold electrons. The charge carriers are the carriers of the heat. The various free electrons in a conductor have a distribution of energy (or temperature). When you apply a potential across the conductor, they all are attracted to the positive end, but the warmest ones tend to have the best success in moving that direction. So in general, heat is carried in the direction of the electron current.

Please understand, this method of explaining these 2 effects is a model which works OK unless you look too hard for the fine details. There's more to it than this.

I hope this helps a bit,
Steve