Which device generates a small voltage when heated due to dissimilar metals?

• A. Thermocouple
• B. Bimetal
• C. Contactor
• D. Pilotstat

Answer: (B)

The key idea is converting a temperature difference between two dissimilar metals into an electrical signal. That’s the principle of a thermocouple. When two different metals are joined and their junctions are at different temperatures, electrons flow and a small voltage is generated. This voltage is what a thermocouple uses to measure temperature; it’s a tiny, precise electrical signal.

A bimetal strip also uses two metals, but for a different effect: because the metals expand differently when heated, the strip bends. That mechanical movement is used for thermostats and temperature controls, not for producing voltage.

The other devices listed are switches or control devices rather than voltage-generating sensors. A contactor is an electrically controlled switch, and a pilotstat is a device that manages the pilot flame—not a voltage source created by heat.

So the device that generates a small voltage when heated due to dissimilar metals is the thermocouple.