How rice cookers know when to stop?

Question

How simple rice cookers (ones with no electronics) know when to stop cooking? My cooker does a pretty good job, and I suspect it is by weight, because when it has no water/no cover the on/off button jumps back to off. However, if it is really based on weight, then how can it know if I have a little rice with water, or a lot of rice and no water?

I am of course talking about an electrical rice cooker. It does not build any steam pressure - so this is not he answer

Answer 1

During cooking the rice/water mixture is heated at full power. The full power temperature cannot go above the boiling point of water (212°F/100°C) as any heat put into the rice/water mixture at that point will only cause the water to boil. At the end of cooking some of the water will have been absorbed by the rice and the rest is boiled off. Once the heating continues past this point, the temperature exceeds the boiling point. The thermostat then trips, switching the rice cooker to low power "warming" mode.

Answer 2

It is temperature. Underneath the bowl is a bi-metal plate attached to a switch. When the rice is boiling the temperature never goes much above boiling point. When the water has evaporated the temperature rises, causing the bi-metal strip to expand and switch off the heater. Most rice cookers than have a second, smaller heater to keep the rice warm. Because the bi-metal switch acts quite quickly, the rice isn't burnt.

Answer 3

what?? a rice cooker with no electricity?? never seen one b4

Answer 4

The time it takes to cook was premeasured and put into the machine

Answer 5

It senses when water is depleted.

Answer 6

Should be the pressure(steam and all).