Question

Why are two different metals used to make a thermocouple?

Answer 1

• Nickle alloy
• platinum rodium alloy
• tungsten
• rheium
• chromel gold iron etc

Answer 2

Thermocouples work based on the principle that each wire will develop a voltage difference along it's length when you heat or cool one end.  Different metals develop different voltages.  Thus, if you connected two different metals and heat the junction, you can measure the voltage difference at the other end, and figure out the temperature.  If both of the wires were the same material, they'd have exactly the same voltage, which means you'd detect no voltage difference at the other end.  That would be useless for measuring temperature.