Thermoelectric series (Seeback series): -
Seeback arranged various metals one after another in a series called as thermoelectric series or Seeback series according as the following:
Sb, Fe, Zn, Ag, Au, Sn, Pb, Cu, Pt, Ni, Bi
He put antimony at the first and bismuth at the last of the series. He put other metals in between antimony (Sb) and bismuth (Bi). According to him, more thermoemf can be produced from the thermocouple of two metals which are more spaced in the series. The maximum thermoemf can be produced from the thermocouple of antimony and bismuth as antimony is the first member and bismuth is the last member of the series that is with maximum separation. Similarly, no thermoemf is produced from the thermocouple of two metals which are placed together in the series.
Seeback also gave the direction of current in the thermocouple. According to him, current flows from the metal occurring earlier to the metal occurring later in the series through the cold junction or from metal occurring later to the metal occurring earlier in the series through the hot junction.
1) In Fe – Cu thermocouple, current flows from copper to iron through hot junction or from iron to copper through cold junction.
2) In Sb – Bi thermocouple, current flows from antimony to bismuth through cold junction or from bismuth to antimony through cold junction.