A current will circulate in a closed circuit comprising two dissimilar conductors if a temperature difference is maintained between the two junctions.
Figure 2 Closed circuit: diagram showing in general terms how a thermocouple works
Broken circuit: heating the junction between the two different metals A and B creates a voltage eAB; it is a function of the temperature at the junction and the composition of the two metals. All dissimilar metals produce this effect.
Figure 3 Open circuit showing in general terms how a thermocouple works
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