Electric kettle that shuts off when boiling

[litup]

Maybe it contains a vibration sensor, the thing does rumble a bit when the water boils. That or the pressure sensor gets my vote. It also has to have by law I think, an over temp switch, the bimetallic unit already mentioned. When that switch heats up too much due to low water, the energy flowing inside the switch causes it to bend when passing a certain temperature, say 120 degrees C, which would never happen if there was water inside, then it bends away from a contact opening the circuit. The best way would be to have a manual reset so a person interacts with it in such a way as it doesn't just recycle itself off and on if left both plugged in with no water and unattended. A simple bi-metallic switch is not smart enough by itself to keep it from just cycling off and on indefinitely when unattended. But if it activates a second circuit that totally shuts down the system, it would never come on again unless you hit a reset button. That keeps people from getting burned or starting fires.

 

[Proton Soup]

Wiki says that they use a bi-metalic switch that bends and cuts off the electricity when the steam warms it up. That explains lisa's double click.

i guess this means there's a lot more heat transferred from steam at the same temperature for this to work. my thermodynamics is pretty rusty, and i never liked it to begin with.

Final temp - initial temp, often you'll see it like T_f - T_i

more or less. but I'm thinking more in terms of something that moves with time, so that you look at the slope of the T(t) curve.
so like delta_T = T(t₂) -T(t₁).

but it sounds like edward dug up the right answer. it'd be simple, cheap, and durable.