OEDILF

Two different metals joined together and heated can produce an electric current. This thermoelectric effect (the Seebeck Effect) is the basis for modern-day applications such as thermocouples and solar panels.

A thermocouple (T/C) is a pair of wires of dissimilar metals or alloys, joined at one end. Since the two metals have different thermoelectric characteristics, there will be a tiny voltage difference between them. By comparing this voltage to the known voltage curve for a specific pair of metals (e.g., NiCr-Ni), the temperature can be determined. T/C's are used extensively in industrial applications (e.g., refineries and specialty chemical manufacturing) to measure the temperature at varying stages of the process.

Two metals with differing thermal expansion ratios are sandwiched into a coin-sized, thin and springy, slightly domed disc. When heated, the inner surface will expand more than the outer one, and the tension makes the dome suddenly turn inside out. A common physics demonstration is having the disc launch itself into the air from a hotplate. If the disc is incorporated in a thermostat, the movement breaks an electric circuit. When the disc cools, it snaps back to its original shape.