The humble old rice cooker, to give us cooked rice with minimal fuss and error. If you’ve ever owned one you know how useful it is. A lot of cookers these days have some circuitry in them that uses fuzzy logic (computer stuff) to determine when rice is cooked, but they both require temperature monitoring so let’s go back to the basics. Have you ever wondered how it knows when to switch off?
Most cookers I’ve seen will switch from cook to warm mode, but some simply turn off, same principle. It’s pretty simple actually.
When you put the metallic bowl of rice and water into the cooker, it sits on a heating element and a thermostat. The heating element obviously heats the container to boil the water, and the thermostat will monitor the temperature and perform an action depending on the temp.
When the water reaches boiling point, the temperature is stable and the boiling is maintained throughout the cooking process as the rice absorbs the water. The temperature is stable thanks to the water being present in the bowl and conducting heat away from the bottom of the container.
Once the rice has absorbed the water and the rest is reduced to steam, the temperature becomes unstable. Without water to boil, only the rice is taking on the heat from the heating element. But because rice is not a fluid, the heat is not easily conducted or dispersed (like it would be in water) and instead the heat builds in the rice very quickly and causes the temperature to rise in the container. The thermostat detects this sudden increase in temperature and initiates the cooker to switch modes from cook to warm or off; if it goes to warm mode then the heating element is set to produce very low heat to maintain warmth.
There you have it. Wonders of engineering!
Originally published at http://haveyoueverwondered123.wordpress.com on March 6, 2022.
