Abstract: In this paper, an expression revealing the physical nature of a fool-work thermocouple is derived. The expression reveals that the e. M. F. Given by a fool-work thermocouple can be regarded as the average e. m. f. Of the divisional thermocouples, in case when all the resistances of all the divisional thermocouples are equal to each other. By considering the factors influencing the contact resistances of a tool-work thermocouple an expression revealing E the e. m. f. given by a fool-work thermocouples in terms of E the e. m. f. producd by the divisional thermocouples and Ari the real contact area , is derived. This expression has been examined by many experiments run by the authors.