The thermocouple among the following that can produce maximum thermo-emf for the same temperature difference between the junction is
a)	Fe-Cu	b)	Ag-Au	c)	Sb-Bi	d)	Cu-Pb

(c)

Seebeck arranged the metals in a certain sequence are called the thermoelectric series.  The direction of current at the hot junction is from metal occurring earlier in series to one occurring later in series.  Some of the substances in series are Bi, Ni, Co, Pd, Pt, Cu, Mn, Hg, Pb, Sn, Au, Ag, Zn, Cd, Fe, Sb, Te.

The more separated the metals are in the series, the greater is the value of thermo-emf generated.  Thus, emf developed in Sb-Bi thermocouple is higher than other thermocouples.