In addition, cables for sockets on a ring or radial main are typically 2.5 mm in diameter. The cross-sectional area of the individual wires within the cable—the actual size of the exposed face of the wire—is measured here. The cable size should be indicated on the sheath. If you need to replace a broken cable, make sure that it's the same size as the original so that there are no short circuits when you connect the new cable to your circuit breaker panel.
Cable sizes are usually expressed in numbers of inches or centimetres. For example, a #6 cable is used to carry a current up to 6 ampeers. A meter can be used to measure the actual size of a cable; it has marks for every 10 inches from 1 to 12 feet. The cable size can then be found by multiplying the number of meters by 0.0254 (which is 4 inches per meter).
Sometimes cable sizes are also described by referring to their outer diameter. For example, a #8 conductor has an outer diameter of 8 millimeters (mm).
The term "conductor" is used for the metal strands inside the cable that transmit electricity. These may be solid or stranded (with or without insulation between the strands). The term does not include any covering or shielding that protects the conductor from damage or contact with other objects. Examples include tape and mesh.
In a 1.5mm cable, the cross-sectional area of the earth wire is 1mm. The measurement of a 2.5mm cable is 1.5mm. Of course, these are average sizes; some cables are smaller and others are larger.
The term "size" of a cable refers to its outer diameter minus its inner diameter. So, for example, a 1.5-mm cable with a outside diameter of 3.5 inches (89 mm) has a total cable diameter of 5.0 inches (127 mm). A 2.5-mm cable with an outside diameter of 4.0 inches (102 mm) has a total cable diameter of 6.0 inches (152 mm).
Cable sizing information can be found in many places. First, it is usually shown on the exterior of the cable sheath somewhere. Second, if you look inside most communications cables you will find that the conductors are insulated from each other by spacers. These are rings of plastic or metal that keep the wires apart at regular intervals along the length of the cable. Each spacer represents one layer of cable insulation, and so multiplying the number of layers by two gives you the overall cable size.
Diameter is a linear unit of measurement. That can't possibly be the same thing. The cable cross-section in square millimeters is not the same as the cable diameter in millimeters. The area of such a cut is referred to as the cross section or cross sectional area. It does not have to be a circle. In fact, it most often is not.
Cable diameter is used to describe the size of a single conductor within a cable. The term is usually applied to describe the outer covering of one or more wires wrapped around a core rather than describing the conductors themselves. For example, an insulated copper wire with a diameter of 1/4 inch (6 mm) would be considered a small cable; two such wires twisted together would be called a light cord; and three such wires wrapping around a plastic tube would be called a ground cable.
Area is used to describe the total surface covered by a system of connected cables or tubings. Area is measured in square meters (m2) or feet squared (ft2). A meter is a distance between two points on a standard measuring rod or ruler. 1 m = 39.37 inches or 100 cm. 1000 m equals 1 km. 10,000 m equals 10 km.
A cable's diameter is its internal dimension. The area of a cable is its external dimension. There is no simple relationship between the two numbers because they describe different things.