the peltier effect,discovered in 1822 is another form of electrical to heat transducer action,and is the reveverse of the thermocouple action.once again,two junction of dissmission metals are used,and in this case,a current is passed around the circuit,resulting in one junction cooling and the other heating.the temperature change for a given current are small for metal-to-metal junction,but can be substantial for metal-to-semiconductor junction,making this auseful way of temperature control for small spaces.