Just as you would expect, there is a multitude of cable types available. For domestic work, however, we need only concern ourselves with a few.
Single core cable
Single core cable is mostly used for industrial applications where it is run in conduits.
In domestic wiring it is usually only used for certain situations. Here they consist of stranded conductors twisted together and housed in a PVC covering. The reason they are manufactured with stranded conductors rather than a solid core is to allow them to be bent easily. A solid core of comparable diameter would be very difficult to work with.
For example, 6 mm sq. single core, colour coded green and yellow, is used for earthing and supplementary bonding. 10mm sq (minimum) single core colour coded green and yellow is used for the main bonding conductors between the earth terminal block in the consumer unit and incoming metal water, gas and oil service pipes. 16 mm sq. single core colour coded green and yellow is used for connecting the earth terminal on the consumer unit to the Company’s earth connection. 16 mm sq. single core which is insulated and sheathed, colour coded brown (old cable colour = red) for live or blue (old cable colour = black) for neutral, is used for the connection of the consumer unit to the meter.
Two core and earth cable
Three core and earth cable
This is similar to two core, but has three conductors, colour coded brown, grey and black (old cable colours = red, yellow, blue) as well as an earth. It is used where two way lighting is needed. It provides the necessary additional conductor between the two switches operating the same light fitting. These colours are for identification purposes only as any, or all, may be live depending on how the circuit is wired.