A fuse is a one time over current protection device employing fusible link that melts after the current exceeds a certain level for a certain length of time. Typically, a wire or chemical compound breaks the circuit when the current exceeds the rated value.
Polyfuse is a new standard for circuit protection .It is resettable. Technically, Polyfuses are not fuses but polymeric positive temperature coefficient thermistors (PPTC). Re-settable fuses provide over current protection and automatic restoration.Recommend this topic