Overheat protection device and varistor

An overheat protection device, comprising:

• a first electrode and a second electrode disposed to be spaced apart;
• a hot-melt wire located between the first electrode and the second electrode, the hot-melt wire being in electrical contact with the first electrode and the second electrode;
• and
• an insulator supporting the first electrode and the second electrode, wherein the hot-melt wire is melted into a liquid hot-melt material when the ambient temperature reaches a predetermined temperature, the liquid hot-melt material wets the first electrode and the second electrode, and the liquid hot-melt material does not wet the insulator at least at a portion located between the first electrode and the second electrode;
• wherein the insulator comprises a cylindrical structure, and the first electrode, the second electrode, and the hot-melt wire are disposed in the cylindrical structure with the hot-melt wire disposed on and in direct contact with an interior surface of the cylindrical structure.