Reversing the heating process

[motorman]

Hi guys,

For today's lunchtime challenge...

If I put 1kw of electrical energy into a heating element and get X amount of heat out, why can't I put ~X amout of heat into the element and get ~1kw of electricity out? ( I accept less than 100% reverse process ability)

what's the mechanism that goes into heating and can it be reversed?

ATB,
motorman

[MagnetDave]

Shortest answer: You can. We do. You just don't get a whole lot.

http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator

[russ_watters]

A heating element works via resistance so it is basically all loss and completely irreversible.

[Naty1]

see here:
http://en.wikipedia.org/wiki/Thermoelectric_effect

and
Thermocouples are widely used to detect the presence of a gas flame....and to shut off the gas supply if the flame is extinguished...At home I have one in my gas water heater and another in my free standing gas fireplace....
http://en.wikipedia.org/wiki/Thermocouple

[motorman]

Thanks for your replies all.

I was thinking Thermocouples would creep in there somewhere, however they need 2 different materials to do the job and a temperature difference to make it(them) work.

I'm thinking about a heating element and how it works. We're taught that it is all about resistance, but what is the actual mechanism at the electron/atom level?