Which statement correctly describes a thermocouple?

Which statement correctly describes a thermocouple?

• A. Made up of two wires of dissimilar metals that measure temperature
• B. Made up of two wires of dissimilar metals that measure pressure
• C. A separate metal that changes resistance with heat
• D. A ceramic sensor that measures humidity

Answer: (A)

A thermocouple uses the Seebeck effect: two wires made of dissimilar metals are joined at one end, and when there’s a temperature difference between that junction and the other ends, a small voltage is generated. That voltage changes with temperature, so the device is used to measure temperature rather than pressure or humidity. This is why the description of two dissimilar-metal wires that measure temperature is the correct one. The other options describe different sensor concepts—pressure measurement with dissimilar metals, a resistance-based sensor like an RTD or thermistor, and a ceramic humidity sensor.

A thermocouple uses the Seebeck effect: two wires made of dissimilar metals are joined at one end, and when there’s a temperature difference between that junction and the other ends, a small voltage is generated. That voltage changes with temperature, so the device is used to measure temperature rather than pressure or humidity. This is why the description of two dissimilar-metal wires that measure temperature is the correct one. The other options describe different sensor concepts—pressure measurement with dissimilar metals, a resistance-based sensor like an RTD or thermistor, and a ceramic humidity sensor.