What happens to thermocouples when there is a greater temperature difference between the junctions?

Thermocouples operate based on the Seebeck effect, where a voltage is generated due to a temperature difference between two junctions made from different metals. The greater the difference in temperature between these two junctions—often referred to as the hot and cold junctions—the higher the voltage output will be. This is because the degree of thermal energy moving through different conductors can create a stronger electric potential difference.

In practical terms, as one junction is heated while the other is kept at a lower temperature, the increase in thermal gradient results in a more pronounced electron flow, thereby increasing the generated voltage. This relationship allows thermocouples to be effective temperature sensors, with their voltage output directly correlating to the temperature differential. Therefore, with greater temperature differences, thermocouples are able to generate more voltage, making option B the correct answer.