The temperature of inversion of a thermocouple is `620^(@)C` and the neutral temperature is `300^(@)C`. What is the temperature of cold junction?

Options

A. `20^(@)C`
B. `320^(@)C`
C. `-20^(@)C`
D. `40^(@)C`

Explanation

To find the temperature of the cold junction (T0) of a thermocouple given the temperature of inversion (Ti) and the neutral temperature (Tn), we can use the relationship between these temperatures.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Temperature of inversion (Ti) = 620°C
- Neutral temperature (Tn) = 300°C

2. **Use the Relationship Between Temperatures:**
The relationship for a thermocouple can be expressed as:
\[ Tn - T0 = Ti - Tn \]
where:
- T0 is the temperature of the cold junction.

3. **Rearranging the Equation:**
We can rearrange the equation to solve for T0:
\[ T0 = Tn - (Ti - Tn) \]
Simplifying this gives:
\[ T0 = 2Tn - Ti \]

4. **Substituting the Known Values:**
Now substitute the values of Tn and Ti into the equation:
\[ T0 = 2(300°C) - 620°C \]

5. **Calculating T0:**
\[ T0 = 600°C - 620°C = -20°C \]

6. **Conclusion:**
Therefore, the temperature of the cold junction (T0) is:
\[ T0 = -20°C \]

### Final Answer:
The temperature of the cold junction is **-20°C**.