Do thermocouples require a power source to operate? If they do, explain or draw a diagram of how a thermocouple is connected to a power source? If they do not explain how a thermocouple operates(you can also include a drawing but you need to explain in words how a thermocouple operates).
No.
Thermocouple is a active device, which produce output voltage on PMMC when two dissimilar metal is connected and one point is connected to reference junction temperature and other at measurement temperature. Hence thermocouple doesn't require any external power.
As we can see from figure, iron and constantan lead are connected together and connected to measurement point and a junction temperature which is usually 0°c. When difference between junction and measured temperature changes then we get output voltage at moving coil instrument. Which is nothing but temperature output.
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