Question

A battery is connected to a thermocouple of copper and iron. The two junctions will be

• A. at the same temperature
• B. heated
• C. neither heated nor cooled
• D. undergoing thermoelectric effect leading to the heating of one junction and cooling of the other

Answer 1

Answer: (D)

undergoing thermoelectric effect leading to the heating of one junction and cooling of the other

When the battery is connected to a thermocouple of copper and iron i.e. current is passed through it, according to Peltier effect the heat is liberated at one junction(it becomes hot) and absorbed at other one(it becomes cold). The direction of thermo-emf is given by the thermoelectric series at given temperature as,
Sb, Fe, Zn, Ag, Au, Mo, Cr, Sn ,Pb, Hg, Mn, Cu, Co, Bi
When a thermocouple is formed using metals in series, the direction of current at the cold junction is from metal occuring earlier in the series to the metal occuring later in it.