What does a thermocouple consist of?

A thermocouple is a device used to measure temperature and is formed by joining two dissimilar wires, known for their different thermoelectric properties. When these wires are connected at one end, they create two junctions: one is the measuring junction, which is placed at the point where the temperature is being sensed, and the other is a reference junction, typically kept at a known temperature.

The fundamental operating principle of a thermocouple is based on the thermoelectric effect, specifically the Seebeck effect, which occurs when there is a temperature difference between the two junctions. This temperature difference generates a small voltage that can be measured and correlated to a temperature reading.

In contrast, the other options do not accurately represent the structure and function of a thermocouple. A thermistor is a different type of temperature sensor that relies on resistance changes; a Wheatstone bridge specifically relates to measuring resistances but is not involved in thermocouples. The mention of a thermally-conductive fluid in a fine tube is more indicative of a thermal expansion device, like a liquid-in-glass thermometer, rather than a thermocouple. Lastly, a setup involving two dissimilar wires connected to a battery does not describe how thermocou