So what’s going on? The kettle in question uses a bimetallic strip, which trips the switch off in the base of the kettle when it gets too hot. There’s also a tube inside the kettle that ...

But the twinkle effect until recently has been hard to describe. Typical flashing bulbs use a bimetallic strip. As the filament of the bulb heats up, the strip bends, opening the circuit.

This video explores heat conduction in brass and iron.