Standard rice cooker uses magnetism to turn off. The steel bowl loses its magnetic attraction when it gets hot - like 400 oC - and it can't get that hot when there's water. Basically, they go full blast until the water boils off, then shut down. As long as the cooker is pretty full, the residual water/steam in the rest of the rice will bring the whole bowl back to 100 oC pretty fast and rehydrate any of the bottom layer that got crispy. If you run a conventional rice cooker under-loaded, you're more likely to get stuck/burned bottom.

I have a cheap, 4 cup rice cooker, but I usually make just 1 cup at a time. Unplug it after 7-12 minutes and it won't burn. I're pretty forgiving. I've used rice cookers from the little 4-cup to big 5-pound commercial cookers. Rice, water to the fingernail/1st joint, go. It's amazing. If you cook rice regularly, just get one.