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In engineering both electrical and electronics, a Fuse is a form of low resistance resistors that acts as a sacrificial device to provide the protection from over Current, of either the load or source circuit. Its vital element is a strip or metal wire that melts when current flows high, which break off the circuit in which it is connected. The main reasons for over current are overloading, Short circuit, mismatched or failure of device.

A flow of over current interrupts by fuse, so that further damage by excessive heating or fire is prevented. Wiring regulation often defines a highest fuse current rating for particular circuits. To limit the human life and electrical device damage over current protection devices are crucial in the systems. All the Fuses are chosen to allow the passage of current a marginal percentage and to allow over current only for tiny periods. Slow blow fuses are allow harmless term larger currents but still clear on a sustained overload. Fuses are manufactured in a ample range of current and voltage ratings and are usually used to protect wiring systems and electrical equipment. Self resetting fuses automatically restore the circuit after the overload has cleared; these are useful, for example, in aerospace or nuclear applications where fuse replacement is impracticable.

Classification of Relays

  1. A protective device that protects an electrical circuit from becoming over loaded. Fuse which contains a length of thin wire (usually of a metal allow) that melts and disconnects the circuit whenever the over current flows through it. They were conventionally used to protect electronics devices / equipment's and prevent fires, have mostly been replaced by circuit breakers.
  2. A cord of readily explosive material that is lighted at one end to carry a flame long its length to explode an explosive at the other end.


 A fuse contains a metal strip or wire fuse element, of less cross section compared to the circuit conductors, mounted between a pair of electrical terminals, and its housings are enclosed by a non combustible material. The fuses are connected in series to carry and pass the current through the circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is (empirically) determined so that the heat for a normal current does not cause the element to achieve a high temperature. If the current flows circuit is high, then the fuse element rises a higher temperature and either melts directly, or else melts a soldered joint within the fuse, to break the circuit.

The fuse element is normally made of zinc, copper, silver, aluminum, or alloys to supply stable and predictable characteristics. The fuse preferably would carry its rated current indefinitely, and melt quickly on a excess. The element must not be damaged by minor harmless surges of current, and must not oxidize or change its behavior after possibly years of service.

The fuse elements may be formed to increase heating effect. In large fuses, current be divided between multiple strips of metal. A dual element fuse may a metal that melts instantly on a short circuit, and also contain a low melting solder joint that to long-term of low values compared to a short circuit. Fuse elements may be supported by steel or nichrome wires, so that no strain is placed on the element, but a spring may be included to increase the speed of parting of the element fragments.

The fuse element may be surrounded by air, or by materials intended to speed the quenching of the arc. Silica sand or non-conducting liquids may be used.  

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