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.
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.
https://youtu.be/RSTNhvDGbYI