PPTC resettable fuses are designed and made of patented novel PPTC material in thin chip form where conductive particles are dispersed in a polymer that has a crystalline structure. At normal operating conditions there are numerous chains forming conductive paths throughout the PPTC material. Under fault conditions (Tripped State), excessive current flows through the PPTC device and the PPTC material heats up. This makes the polymer matrix's morphology change from crystalline to amorphous. Under these conditions the conductive particles move apart from each other, most of them no longer conduct current and the resistance of the device increases sharply. Upon the fault current being removed, the resettable fuse is reset and allows the current through the circuit again.