Question

One junction of thermocouple is at $0^{0}C$ and the other junction is heated. Maximum current in the thermocouple is observed when hot junction is at ${240}^{0}C$. The temperature of the hot junction at which the direction of current reverses is

• A. ${240}^{0}C$
• B. ${480}^{0}C$
• C. ${360}^{0}C$
• D. ${120}^{0}C$

Answer 1

Answer: (B)

${480}^{0}C$

If $T_c$ is the temperature of cold junction, $T_i$ be the inversion temperature and $T_n$ be the neutral temperature,

Then, $T_i=2T_n-T_c$

Here, $T_c=0^{o}C$ and $T_n={240}^{o}C$

The current direction reverses at inversion temperature $T_i$.

So, $T_i=2\left(240\right)-0={480}^{o}C$