The thermo e.m.f. E in volts of a certain thermocouple is found to vary with temperature difference θ in ⁰C between the two junctions according to the relation
E = 30θ – θ² / 15
The neutral temperature for the thermocouple will be

Options

(a) 30⁰C
(b) 450⁰C
(c) 400⁰C
(d) 225⁰C

Correct Answer:

225⁰C

Explanation:

E = 30θ – θ² / 15
For neutral temperature, dE/ dθ = 0
0 = 30 – 2/15 . θ
θ = 15 x 15
= 225⁰C