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If the cold junction of a thermo-couple is kept at $0^\circ C$ and the hot junction is kept at $T^\circ C$, then the relation between neutral temperature ($T_n$) and temperature of inversion ($T_i$) is
A
$T_n = 2T_i$
B
$T_n = T_i - T$
C
$T_n = T_i + T$
D
$T_n = \dfrac{T_i}{2}$
Detailed Solution
The thermo emf of a thermocouple varies parabolically with the temperature of the hot junction.
The neutral temperature $T_n$ is the temperature at which the thermo emf is maximum; the temperature of inversion $T_i$ is the temperature at which the emf becomes zero again and reverses.
Because the curve is a symmetric parabola, the neutral temperature lies midway between the cold junction temperature $T_c$ and the inversion temperature: $T_n = \dfrac{T_i + T_c}{2}$
Here $T_c = 0^\circ C$ = temperature of the cold junction.
$T_n = \dfrac{T_i + 0}{2}$
$T_n = \dfrac{T_i}{2}$
The neutral temperature $T_n$ is the temperature at which the thermo emf is maximum; the temperature of inversion $T_i$ is the temperature at which the emf becomes zero again and reverses.
Because the curve is a symmetric parabola, the neutral temperature lies midway between the cold junction temperature $T_c$ and the inversion temperature: $T_n = \dfrac{T_i + T_c}{2}$
Here $T_c = 0^\circ C$ = temperature of the cold junction.
$T_n = \dfrac{T_i + 0}{2}$
$T_n = \dfrac{T_i}{2}$