The thermo e.m.f E in volts of a certain thermocouple is

The thermo e.m.f E in volts of a certain thermocouple is found to vary with temperature difference θ in °C between the two junctions according to the relation
E - 30θ - θ²
15

The neutral temperature for the thermocouple will be

E = 30Ω -	θ²
	15

For neutral Temperature, de/dθ = 0
0 = 30 - (2/15)θ
∴ 0 = 15 x 15 = 225° C
Hence, neutral temperature is 225°C.

E - 30θ -	θ²
	15