# Ising model

People always talk to me that Ising model to the statistical mechanics is like the hello world program to the computer science. For me, I majored in electronic information engineering when I was in college. I didn't take the courses as a physics students did. Now I work as research assistant at the Institute of Applied Physics and Materials Engineering, University of Macau. There are lots of terms new to me. So I decided to learn them one by one. Today, I'm going to learn the first one: Ising model.

I like to learn from example and from something I familar with. First, I would like to ask a question. Why the rice cooker know the rice is ready to eat and stop heating? Not long time ago, I naively thought there should be a temperature sensor connected to a microcontroller inside the rice cooker. When most of the liquid water is vaporized, the temperature will greater than a threshold set by by the microcontroller, then trrigers a signal to stop heating, such as, a programm like this.

while True:
temp = readTempFromSensor()
if temp > 120:
stopHeating()
break()
else:
Heating()

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To my surprise, when I learn more about rice cooker, I was astonished by its simple and elegant machanism. There is a magnet inside the rice cooker. When this magnet is heated above 100°C, which means there is no liquid water in the rice cooker, the magnet will lose its magnetism. This will trigger the rice cooker change from cooking to keep warm, and stop heating.