What does a thermocouple produce when heated?

When heated, a thermocouple produces a voltage that correlates with the temperature difference between its two junctions. This phenomenon is based on the Seebeck effect, where the junctions of two different metal wires generate a small voltage when there is a temperature gradient between them. The amount of voltage produced is directly related to the temperature difference, making it an effective and widely used method for measuring temperature.

The generated voltage can then be interpreted by connecting the thermocouple to a measuring instrument that can convert this voltage into a temperature reading. This principle is what makes thermocouples valuable for a variety of heating and temperature monitoring applications in many industries, including electrical utility work where linemen may encounter such devices during their tasks.

While other options suggest signals or currents in relation to temperature or pressure, they misrepresent the function of a thermocouple specifically, which is to generate a measurable voltage as a response to temperature differences.