9.1: Conductors
A material that allows energy to flow with relative ease is known as a conductor . The most common form of electrical conductor used is the wire. Most electrical wires are made from copper or aluminum and are in one of two forms: solid or stranded.
The term electrical cable usually refers to multiple insulated wires grouped in a common sheathing (Figure \(\PageIndex{1}\)).
Stranded conductors
Stranded wire is a collection of solid wires twisted or braided together, commonly around a central core (Figure \(\PageIndex{2}\)).
The current carrying capacity of a stranded wire is close to the current carrying ability of a single strand. Stranded wires act as a single conductor and carry a single electrical current. Stranded conductors are normally used in a thin wire that requires flexibility, such as speaker wire. Ordinarily, a stranded conductor has wires all the same size. The size of the strands used depends on the flexibility required. For example, #00 gauge cable may be made up of seven strands of #7 gauge wire, or 19 strands of #12 gauge, or 37 strands of #24 gauge, the last one being rated “extra flexible.”
Solid conductors
Solid wire consists of one strand of copper metal wire, bare or surrounded by an insulator. Solid wire is normally found in smaller sizes only. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire.
Insulating materials
The purpose of conductor insulation is to prevent unwanted flow of electrical current, such as ground faults, short circuits, or electric shock. There are various methods used to insulate conductors to satisfy the many conditions encountered in electrical installations, such as temperature, moisture, and different voltage
ratings. Insulating materials include:
- enamel coating
- rubber
- thermoplastics
- minerals
Stripping insulation
To make any type of electrical connection, you will need to expose the base wire from
the insulated covering. You can do this with wire strippers (Figure \(\PageIndex{3}\)).
With wire strippers, you can strip the amount of wire required for the type of connection being made. It is important to avoid damaging the copper wire by nicking the copper or cutting into it. Nicked wires can lead to overheating and eventually could cause an electrical fire.
Colour coding
Most electrical wiring circuits look complicated because several wires are found at any one point in the circuit. To make it easier to know exactly which is which, wires are identified by colour or labeled.
For building construction, the Canadian Electrical Code reserves two colours for specific applications:
When this system of colour coding is followed, at any point in any circuit, a white wire always indicates a neutral conductor. A green wire always indicates an equipment grounding conductor. Any other colour wires, such as red, black, or blue, can be assumed to be live or hot, meaning that they will have a voltage on the conductor and are therefore dangerous.
Wire size
Wires are manufactured in sizes according to the American Wire Gauge (AWG) system. The cross-sectional area of each gauge is an important factor for determining the current carrying capacity of a wire (ampacity). Increasing gauge numbers denote decreasing wire diameters, ranging from the largest 0000 (4/0) to the smallest, 44.
- White or natural grey covering is reserved for insulated, identified conductors, identified common conductors, and identified neutral conductors.
- Green covering is reserved for the equipment grounding conductor.