A device that uses dissimilar metals to control electron flow is known as a

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

Answer: (C)

Dissimilar metals joined at a junction form a thermocouple. When the two metals experience a temperature difference between the junctions, electrons move and generate a small voltage through the Seebeck effect. That voltage provides a temperature-dependent electrical signal, which is how thermocouples are used for sensing or controlling temperature. This is different from a thermistor, which changes resistance with temperature; an RTD, which relies on the resistance change of a single metal; or a capacitor, which stores charge and does not generate a temperature-dependent voltage from metal junctions. Therefore, the device described is a thermocouple.