Glossary:Polyfuse
A polyfuse or polyswitch or polymeric positive temperature coefficient (PPTC) device is an alternative to a conventional fuse for protection against a dangerously large current flow in a fault condition. It consists of a polymer loaded with carbon particles. An excessive current causes it to heat up and the polymer to expand so that the carbon particles are no longer in contact. As a result, the current can no longer flow until it's allowed to cool down. See Polyfuses in the Wiki.