During the gradual rise of temperature, when the temperature reaches the soft magnetic Curie point temperature, the soft magnet changes from a magnetizer to a non-conducting magnet, and the soft magnetic magnet loses its magnetic permeability. At this time, the soft magnetic force is caused by the internal spring force. Separated from the hard magnetic, the pull rod pushes the mechanical switch at the bottom of the pot, and the heating circuit is powered off, thereby achieving the purpose of controlling the temperature.