A fuse is an electrical safety device that operates to provide over-current protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. Once a fuse has blown, it must be replaced or rewired, depending on the type. There are thousands of different fuse designs which have specific current and voltage ratings, breaking capacity and response times, depending on the application. The time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption. The speed at which a fuse blows depends on how much current flows through it and the material of which the fuse is made. The operating time is not a fixed interval, but decreases as the current increases. Fuses have different characteristics of operating time compared to current. A standard fuse may require twice its rated current to open in one second.
A "holder" is a device or implement for holding, storing, or securing something. It may be a container or receptacle, a rack or rest, or even a bracket or screw.