Question

For a thermocouple, the neutral temperature is $270{^\circ}C$ and the temperature of its cold junction is $20{^\circ}C$. If there is no deflection in the galvanometer, the temperature of the hot junction should be

• A. $210{^\circ}C$
• B. $540{^\circ}C$
• C. $520{^\circ}C$
• D. $209{^\circ}C$

Answer 1

Answer: (C)

$520{^\circ}C$

Answer 2

When there is no deflection, then this temperature is called inversion temperature. It is given by the relation $\theta_{n} = \frac{\theta_{i} + \theta_{c}}{2}$

Where $\theta_{c}$ is temperature of cold junction $= 20^{o}C$ and neutral temperature $\theta_{n} = 270^{o}C$

$\therefore$ $\theta_{i} = 2\theta_{n} - \theta_{c} = 540 - 20 = 520^{o}C$