Old-fashioned rice cookers are extremely clever

Have I got the channel for you! Technology Connections: [LINK] . My introduction was his rice-cooker video: [VIDEO] .

The science behind a rice cooker is fascinatingly clever, yet painfully simple. In short, boiling water temperature plateaus due to the latent heat of vaporization. When the water is gone the temperature of the pot starts to rise. The rice cooker uses this principle to control the switch. The switch is held by magnet. When the pot finishes boiling the heat rises and exceeds the curie point of the magnet, which means the magnet ceases to be magnetic, and the (no longer) magnetic switch is released turning the rice cooker off. Here’s a great video explaining how it works. [VIDEO]

I started using the old-fashioned analogue rice cooker after watching Technology Connection's video on how they work. The principle is clever: liquids at boiling point stay at boiling point, since any additional heat energy is used to change their state from liquid to gas. When the temperature does rise above 100°C, that means there is no liquid left in the cooker, and so rice must be done. It then switches off the high heat and runs in "warm" mode. 1. [VIDEO]

I have a basic rice cooker and I absolutely love it. Perfect rice every time without having to think too hard about measurements or the time, as the measurements are stamped on the bowl (fill rice here, fill water here) and it will always switch to warming mode at exactly the right time. I wouldn't bother getting a fancy computerized model, the old thermostatic ones are pretty much perfect. Technology Connections video on old-style rice cookers: [VIDEO] We have that exact same kettle, its wonderful.

It's a great channel. I was also fascinated by his rice cooker episode. I had no idea they were so clever, combining thermodynamics and the physics of magnetism. [VIDEO]

No, the most basic rice cookers are very simple. They use a spring-actuated switch and a magnet paired with an alloy button in contact with the bottom of the cooking bowl that has a Curie temperature just slightly above the boiling point of water. When the rice has absorbed all the water the temperature can finally begin to exceed boiling and the button heats up with it, causing the magnet to lose attraction to it. When the magnet is no longer able to overpower the spring, the switch opens and cooking is shut off (usually into a low power keep-warm setting) [1]. [1] [VIDEO]

I love rice cookers! Rice cookers (usually) make clever use of 1) alloys whose magnetism depends on temperature and 2) the fact that boiling water occurs at a fixed temperature. With a "trigger" temperature just above the boiling point of water, the rice cooker automatically turns off the heating element when all the water is gone (and thus the temperature starts to rise above boiling point). More detail here: [VIDEO]

> weight/balance mechanism in a traditional "dumb" rice cooker These are far more interesting than that. Technology Connections YouTube channel did a great breakdown of how they really work: [VIDEO]