1. History
o The first electrical power in homes was used to power electric lights. This method was called knob and tube wiring. The wiring consisted of a solid copper conductor that was insulated with a thick wrap of brown paper. The paper insulation was then covered in a thin layer of cotton thread. Knobs made of porcelain were nailed on walls and rafters to support the wire. Tubes of porcelain were used as insulators when the wire ran between finished floors. This type of wiring was so well done, that it can still be found in older homes today, and the installation methods are still approved by modern electrical codes.
Function
o All wiring, regardless of size, carries electrical signals. A main component of all wiring is the electrical conductor, or the wire itself. Outside of that wire is an insulation to protect the conductor. This insulation can be made from many types of plastic or fiber, depending on the end use and environmental conditions. Wires placed in a high temperature setting such as a stove or oven will have insulation fibers that resist high heat. In very cold climates, wires have extremely flexible plastics for the outer covering. This covering can resist cracking at low temperatures and can be used in freezers or refrigerators.
Types
o Aluminum at one time was used for house wiring. But aluminum wire heats and contracts when conducting electricity, causing loose wires that pose a fire risk. Since that time, aluminum wiring has been confined, for the most part, to the wires used for bringing in the electrical power to the meter pole. Copper wire is now the norm for all electrical wiring that carries power throughout the home (see Resources below). Special applications for precision signal carrying in audio and video feeds may use gold plating, which is an excellent conductor, for the plugs on stereo or DVD players.
Size
o Wiring comes in many sizes depending on the amount of power it is intended to carry. The lines that bring in the electrical power to your home are about the diameter of your thumb. The copper wires that power the stove and dryer in your house are the size of a thick pencil. These type of wires can be a stranded wires, which are an assembly of solid wires that are wound around a central wire. This allows the conductor to carry more electricity. Wires that carry the video signal to your computer monitor are made up of many insulated wires placed inside an overall plastic jacket. The entire assembly of wires may also be surrounded by a wire braid called a grounding jacket or shield. This shield is placed just under the overall plastic jacket. The shield keeps other electrical signals from interfering with the monitor's picture.
