There used to be a demo in Epcot (‘The Body’?) which had two coils, one cold and one heated.. they were separate at the ends, so you could feel the difference.

There used to be a demo in Epcot (‘The Body’?) which had two coils, one cold and one heated.. they were separate at the ends, so you could feel the difference. In the middle, they were interleaved, and if you put your hand on it, it would feel simultaneously hot and cold. Cool demo.