# Question about the existence of a certain kind of chip **URL:** \ **Category:** Factual Questions\ **Created:** [October 25, 2004, 5:46am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009 "2004-10-25T05:46:51Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![lukaspriest](https://avatars.discourse-cdn.com/v4/letter/l/b5a626/32.png) [@lukaspriest](https://boards.straightdope.com/u/lukaspriest)\ **Post date:** [October 25, 2004, 5:46am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009/1 "2004-10-25T05:46:51Z")
Anyone out there know of some kind of chip/component (or whatever you’d call it) that becomes cold when electricity is passed through it one way and warm/hot when current is passed through it the other way? Or something like that…I don’t have the engineering background to be more specific… ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 25, 2004, 5:59am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009/2 "2004-10-25T05:59:57Z")
It’s not a chip, exactly, it’s an array of thermocouple junctions called a [Peltier effect device](http://www.fact-index.com/p/pe/peltier_effect_1.html). Places like American Science and Surplus have them you can play around with for around $20 or so. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 25, 2004, 6:09am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009/3 "2004-10-25T06:09:35Z")
[Here you go](http://www.sciplus.com/singleItem.cfm?terms=9596&cartLogFrom=Search). ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [October 25, 2004, 6:14am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009/4 "2004-10-25T06:14:26Z")
Two things to keep in mind about these things: Make sure you properly heatsink the hot side (Fans are a good idea, too) and watch the power requirements. Some of these have low voltage and high current requirements to operate to specs. They’re neat to play with, though. They really do get quite cold. ---
**Author:** ![Phnord\_Prephect](https://avatars.discourse-cdn.com/v4/letter/p/df705f/32.png) [@Phnord\_Prephect](https://boards.straightdope.com/u/Phnord_Prephect)\ **Post date:** [October 25, 2004, 10:57am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009/5 "2004-10-25T10:57:48Z")
Wow, this is interesting indeed: > [@](#): > > Apply heat or cold to the relevant face and produce a current How the heck does this thing work, anyway? What’s the physics behind it? My ignorant laymans mind assumes that any current will produce heat, it’s that whole laws-of-thermodynamics thing. Of course the ‘hot’ side probably gets hotter than the ‘cold’ side gets cold, but how? And what if you applied heat to one side and cold to the other… can you generate twice as much current? I gotta get me one of these things! ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 25, 2004, 11:11am UTC](https://boards.straightdope.com/t/question-about-the-existence-of-a-certain-kind-of-chip/271009/6 "2004-10-25T11:11:12Z")
> [@Phnord Prephect](#): > > Of course the ‘hot’ side probably gets hotter than the ‘cold’ side gets cold, but how? I can’t explain the physics of it but yes; the heat output is equal to the heat energy pumped out of the cold side, PLUS the energy consumed by running the device. > [@](#): > > And what if you applied heat to one side and cold to the other… can you generate twice as much current? Yes, in fact it is necessary; rather than specifically applying heat or ‘cold’, you actually have to provide a _temperature difference_ - this could be done by sticking one side to a hot object and heatsinking the other, or it could be done by sticking the heatsink in ice cold water and leaving the other side exposed to warm air. In any situation where there is a temperature difference, heat can be transferred from the hot body to the cold one - the Peltier effect device simply makes it do some work on the way. One of the most common applications for this device is picnic boxes - they have a peltier device and a 12v car lighter plug - you plug it in and the contents will be cooled to (something like) 20C below the ambient temperature. If you reverse the polarity of the supply, the contents will be kept warm instead.