It's basically the same physics involved in this toaster https://youtu.be/1OfxlSG6q5Y same channel.
Thing heats and deforms (change properties), when it reaches temperature n, thing deforms just a bit too much, cuts electrical contact.
Thing heats and deforms (change properties), when it reaches temperature n, thing deforms just a bit too much, cuts electrical contact.
(I have one of those toasters, and they’re very pretty and charming to see work.)