Why does a thermocouple generate voltage?

A thermocouple generates voltage due to the phenomenon called the Seebeck effect, which occurs when there is a temperature difference between two dissimilar metals joined at one end. When heat is applied to the junction of these metals, it creates a change in temperature that causes a differential in electron movement across the materials, leading to the generation of a voltage.

The reason heat causes the metals to expand and generate voltage ties into the principle that the increased thermal energy causes charge carriers within the metals (usually electrons) to move more freely. This movement creates an electromotive force, resulting in the voltage output.

Understanding this principle is crucial as it highlights how thermocouples can be used in temperature measurement and control applications, leveraging the relationship between temperature change and electrical voltage generation. This functionality is what makes thermocouples valuable in various industrial and scientific applications.