Which of the following statements about thermocouple systems is true?

Thermocouple systems are devices used to measure temperature based on the thermoelectric effect, which generates a voltage when two dissimilar metals are joined and exposed to a temperature gradient. The correct statement is that they respond to rapid changes in temperature. This responsiveness is due to the fact that thermocouples generate a voltage that reflects the temperature difference at the junctions, allowing them to quickly detect and react to fluctuations in temperature.

Thermocouples are not limited to high-temperature activation, as they can function effectively across a wide range of temperatures, including very low temperatures. While their speed of response can vary with specific types, they generally respond faster than thermal switch systems, which often involve moving parts and can have delays due to the physical mechanisms involved. Thermocouples also do not operate solely on mechanical principles; they rely fundamentally on electrical principles as they measure voltage generated by temperature differences, distinguishing them from purely mechanical devices.