Question

In Sb-Bi thermocouple, beyond the inversion temperature at cold junction, electric current flows from:

• A. Sb to Bi
• B. Bi to Sb
• C. No current flows
• D. Maybe in any direction

Answer 1

The correct option is B Bi to Sb

When two metals in a thermoelectric series form a thermocouple, there is a flow of current from the cold junction from the metal appearing on the top of the series to the metal appearing at the bottom of the series.

And we see that for a given temperature difference farther metals can produce a larger emf. For example Sb-Bi (Antimony-Bismuth) shows a larger e.m.f for a given temperature difference.When the temperature of the cold junction(Sb-Bi ) is increased there is temperature inversion and current reverses direction from Bi to Sb