Variation of Thermo-Emf with Temperature #8211; In a thermocouple as the temperature of the hot junction at constant temperature (say 0° C), the thermo-emf increase till it becomes maximum at a certain temperature. (i) Thermoelectric emf is given by the equation E = αt + 1/2βt<sup>2</sup> i.e. α + βt<sub>n</sub> = 0 ⇒ -α/β (ii) Neutral temperature is independent of the temperature of cold junction, (iii) Relation between t<sub>n</sub>, t<sub>i</sub> and t<sub>c</sub> is t<sub>n</sub> = t<sub>i</sub> + t<sub>c</sub>/2, (iv) At neutral temperature, thermoelectric power is zero.