Curie-ous about rice cookers?
How does a rice cooker know when the rice is done?
You can buy a rice cooker for about £20[1] and they cook rice perfectly. How do they magically know that the rice is cooked though?
It's actually a very clever piece of technology that uses the concept of the Curie point, where certain materials lose their magnetism at specific[2] temperatures. The steps are:
- Placing a filled pot of rice onto the rice cooker presses down the spring-loaded base.
- This movement attaches a permanent magnet to an alloy with a specific Curie point, completing the circuit that powers the heating element.
- The cooker then starts heating up.
- Since water boils at 100°C under normal atmospheric pressure, the temperature of the water and the pot won’t rise significantly beyond that, as any excess heat is released as steam.
- Once the water is either fully absorbed or evaporated, the temperature of the pot rises quickly. This increase in temperature reaches the Curie point of the material used in the magnet.
- At this point, the alloy to which the magnet is attached loses its magnetism[3], causing the circuit for the heating element to disconnect.
- The rice is done.
A great youtube video explaining this is here.
