Short answer — the internal “switch” is held in the on position by a magnet. Magnets become much less effective when they get hot, and while there is still water in the cooker the maximum temperature will be 100C. Once all the water boils off the temperature quickly rises — but the magnets stop being able to attract the switch when they hit around 102 - 103C or so and release the switch, turning the machine off.
So all has is a switch connected to a magnet next to the bottom of the pot. That’s it. Physics does the rest.
Most thermostats in electronics such as kettles and cookers use a bi-metallic strip inside, where the two metal layers expand at different rates.
The contacts in the switch are physically pulled apart by the strip bending when the desired temperature is reached.
https://en.m.wikipedia.org/wiki/Bimetallic_strip
Not sure where they said they “did an entire presentation on this thing” or where they got their information from.
I’m only adding some context to what I know of how thermostats work. I would gladly admit I’m wrong if provided with some evidence.
If you want a visual demonstration of a thermostat working here’s a video.
(For context I don’t mean to come across as one of those “well ackshually” asshats, I just like watching people take apart electronics (was also slightly obsessed with magnets as a kid. MANY hard drives were sacrificed to my curiosity lol).)
rice cookers depend on the curie temperature of magnets rather than bimetallic strips because the way you want them to work is to pump full power into the pot until all water has boiled off, at which point they should instantly switch off to stop the rice from burning. a bimetallic strip bends over a range of temperatures, but the magnetic switch in the rice cooker snaps open the instant the target temperature is exceeded and doesn’t automatically reset. that’s the big one.
See I thought the curie temperature was a ‘one and done’ sort of deal where you have to go through the process of remagnetizing the magnet after it had gone beyond that point.
it is, for permanent magnets. but for things attracted to permanent magnets, it’s not. so the permanent magnet is shielded from the heat while the metal alloy piece in contact with the bowl is allowed to heat up.
And how do they work?
Short answer — the internal “switch” is held in the on position by a magnet. Magnets become much less effective when they get hot, and while there is still water in the cooker the maximum temperature will be 100C. Once all the water boils off the temperature quickly rises — but the magnets stop being able to attract the switch when they hit around 102 - 103C or so and release the switch, turning the machine off.
So all has is a switch connected to a magnet next to the bottom of the pot. That’s it. Physics does the rest.
https://en.m.wikipedia.org/wiki/Curie_temperature I doubt they’re using magnets, especially considering how hot they have to get to lose their magnetism as you suggest.
Most thermostats in electronics such as kettles and cookers use a bi-metallic strip inside, where the two metal layers expand at different rates. The contacts in the switch are physically pulled apart by the strip bending when the desired temperature is reached. https://en.m.wikipedia.org/wiki/Bimetallic_strip
responding to someone going “i researced and did an enhire presentation on this thing” with “well wikipedia says you’re wrong” is peak internet.
the answer was from a different person who made the presentation
accusing the wrong person is also peak internet
Not sure where they said they “did an entire presentation on this thing” or where they got their information from. I’m only adding some context to what I know of how thermostats work. I would gladly admit I’m wrong if provided with some evidence.
If you want a visual demonstration of a thermostat working here’s a video.
https://youtu.be/eRnYp8foJks
(For context I don’t mean to come across as one of those “well ackshually” asshats, I just like watching people take apart electronics (was also slightly obsessed with magnets as a kid. MANY hard drives were sacrificed to my curiosity lol).)
yeah we went over that in another sub-thread.
regarding the actual info, fittingly alec of technology connections has also made a video on rice cookers! it’s a short one by his standards, but in case you’re not able to watch:
rice cookers depend on the curie temperature of magnets rather than bimetallic strips because the way you want them to work is to pump full power into the pot until all water has boiled off, at which point they should instantly switch off to stop the rice from burning. a bimetallic strip bends over a range of temperatures, but the magnetic switch in the rice cooker snaps open the instant the target temperature is exceeded and doesn’t automatically reset. that’s the big one.
Oh nice one, that’s kinda cool
See I thought the curie temperature was a ‘one and done’ sort of deal where you have to go through the process of remagnetizing the magnet after it had gone beyond that point.
it is, for permanent magnets. but for things attracted to permanent magnets, it’s not. so the permanent magnet is shielded from the heat while the metal alloy piece in contact with the bowl is allowed to heat up.
They do the thing until the thingymajogger flips, obvs.
Funny you should ask https://youtu.be/RSTNhvDGbYI