What device uses dissimilar metals to generate a voltage proportional to temperature?

• A. Thermistor
• B. Thermocouple
• C. RTD
• D. Diode

Answer: (B)

A thermocouple operates on the Seebeck effect: when two different metals are joined, a voltage is generated between the free ends that is proportional to the temperature difference between the junctions. This means the device uses dissimilar metals to produce an electrical signal that reflects temperature. The voltage is small and depends on which metals are used (different metal pairs have different sensitivities), and you typically compare the measurement junction to a known reference (cold-junction compensation) to deduce the actual temperature. Other sensors don’t rely on dissimilar metals producing an emf: thermistors and RTDs are resistance-based sensors using the same material whose resistance changes with temperature, while a diode’s temperature effect comes from semiconductor behavior, not a pair of dissimilar metals.