Which statement best describes the Seebeck effect used in thermocouples?

• A. The Seebeck effect generates a voltage in response to temperature differences.
• B. Humidity changes affect readings.
• C. Pressure variations change the output.
• D. Magnetic fields induce voltage in thermocouples.

Answer: (A)

The Seebeck effect is the generation of an electromotive force when there is a temperature difference across two dissimilar conductors. In a thermocouple, two different metals are joined to form a hot junction and a separate reference junction. Because each metal has a temperature-dependent Seebeck coefficient, the difference between those coefficients produces a net voltage that is proportional to the temperature difference between the junctions. This voltage is what the thermocouple measures and converts into a temperature reading. Humidity, pressure, or magnetic fields don’t create this thermoelectric voltage in a thermocouple, so they don’t describe how the Seebeck effect works.