Q. The temperature of cold, hot junction of a thermocouple is $0℃\ and\ T℃\ $respectively. The thermo-emf produced is $E = AT - \frac{1}{2}\ BT^{2}.$ If $A = 16,\ B = 0.08$0, the temperature of inversion will be
A) $100℃$
B) $300℃$
C) $400℃$
D) $500℃$
Explanation
(c) Let temperature of cold junction be $0℃$ and that of hot junction be $T℃.$ The relation for thermo-emf is given by
$E = AT - \frac{1}{2}\ BT^{2}$
Given, $A = 16,\ B = 0.08$
$\therefore E = 16T - \frac{1}{2} \times 0.08 \times T^{2}$
Since, at temperature of inversion emf is zero, we have
$0 = 16T - 0.04\ T^{2}$
$\Rightarrow T = \frac{16}{0.04} = 400℃$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.