Q. The thermo e.m.f. E in volts of a certain thermo-couple 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 thermo-couple will be
A) 450°C
B) 400°C
C) 225°C
D) 30°C
Explanation
[Solution from source] Neutral temperature is where E is maximum: dE/dθ = 30 − 2θ/15 = 0, so θ = 225°C. 450°C is the temperature of inversion (twice the neutral temperature), where E becomes zero again. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.