Which of the following describes the purpose of a thermocouple?

A thermocouple is a device used primarily to measure temperature. It consists of two different metals joined at one end, creating a junction that generates a small voltage when subjected to a temperature difference. The generated voltage correlates to the temperature difference between the hot junction (where the metals are joined) and the cold junction (the reference point for temperature measurement).

While the primary function of a thermocouple is to measure temperature, it does so by generating a voltage, which is crucial for determining the temperature based on thermoelectric principles. This output can then be read by a multimeter, indicator, or control system to provide an accurate temperature measurement. Therefore, stating that the purpose of a thermocouple is to generate voltage captures its operational principle while relating directly to its function in temperature measurement.

The other options mention functions that are unrelated to what a thermocouple does. Measuring temperature differences is part of its function, but the question specifically refers to its purpose, which is more accurately linked to the generation of voltage for measurement purposes. The conversion of AC to DC and increasing current flow are functionalities associated with completely different electrical devices, making those options irrelevant in this context.