Junction Box

An electrical junction box is a container for electrical junctions, usually intended to conceal them from sight and to some extent to eliminate tampering. It can be a small metal or plastic container, such as those intended to form part of wiring, especially in buildings; in this type of application, it may form part of an electrical conduit wiring system, or may be buried in the plaster of a wall, concealed behind an access panel or cast into concrete with only the lid showing. It may or may not include terminals etc. for joining wires. A similar container used for joining wires to electrical switches or sockets is called a pattress.

Junction boxes form an integral part of a circuit protection system. In the event circuit integrity has to be provided, as may be necessary for emergency lighting or emergency power lines, or the wiring between a nuclear reactor and a control room. In such an event, the fireproofing afforded to the incoming or outgoing cables must also be extended to cover the junction box to prevent short circuits inside the box during an accidental fire. Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to describe common features of electrical wiring that should apply worldwide.

A cable is two or more wires or ropes running side by side and bonded, twisted or braided together to form a single assembly. In mechanics, cables are used for lifting and hauling; in electricity they are used to carry electrical currents. An optical cable contains one or more optical fibers in a protective jacket that supports the fibers. Mechanical cable is more specifically called wire rope. Cables can be securely fastened and organized, such as by using cable trees with the aid of cable ties or cable lacing. Continuous-flex or flexible cables used in moving applications within cable carriers can be secured using strain relief devices or cable ties. Copper corrodes easily and so should be layered with Lacquer.

A short circuit in an electrical circuit is one that allows a current to travel along a different path from the one originally intended. The electrical opposite of a short circuit is an "open circuit", which is an infinite resistance between two nodes. It is common to misuse "short circuit" to describe any electrical malfunction, regardless of the actual problem. In circuit analysis, the term short circuit is used by analogy to designate a zero-impedance connection between two nodes. This forces the two nodes to be at the same voltage. In an ideal short circuit, this means there is no resistance and no voltage drop across the short. In simple circuit analysis, wires are considered to be shorts. In real circuits, the result is a connection of nearly zero impedance, and almost no resistance. In such a case, the current drawn is limited by the rest of the circuit.