Q. The thermo emf of a thermo-couple is found to depend on temperature $T$(in degree Celsius) as $E = 4T - \frac{T^{2}}{200},$ where $T℃$ is the temperature of the hot junction. The neutral and inversion temperature of the thermocouple are (in degree celsius)
A) 100, 200
B) 200, 400
C) 300, 600
D) 400, 800
Explanation
(d) $\frac{dE}{dT} = 4 - \frac{2T}{200}4 - \frac{T}{100};$
At neutral point, $T = T_{n}.$
$\frac{dT}{dT} = 0 = 4 - T_{n}$/100
or $T_{n} = 400℃,\ T_{i} = 2T_{n} - T_{0}$
$\ \ = 2 \times 400 - 0 = 800℃$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.