For individuals not trained as electricians, understanding electrical wiring can sometimes be a challenge. Part of this is that the jargon used to describe electrical systems and their components requires a bit of background to understand properly. Electrical wires come in a large variety of sizes, as well as being made of different materials. You might see an electrical wire made of a single metal strand, or find that a “wire” contains a great number of small strands bundled together. Here I will attempt to explain why these variations exist, how to tell the differences between them, and what functions they serve.
Size
The most obvious distinction you might notice in wiring is size. We refer to different wire sizes as being different gauge wire. For example, 12 gauge wire is thicker in diameter than 16 gauge wire, which is in turn thicker than 24 gauge wire. Choosing your gauge is a matter of balancing cost with effectiveness. Wiring with a thicker diameter (or lower gauge number) will have less resistance to electrical flow than thinner wire. Not only will this mean that less energy is lost over the length of transmission, but that more power can be transmitted safely. Lost energy doesn’t just mean a higher bill, this energy is normally released as heat. Attempting to transmit a large amount of energy through a thin wire will mean that a lot of heat is produced, potentially melting the wire, starting a fire, or causing other damage. Wire which has a larger diameter has the benefit of not only losing less of the energy it carries, but also being able to carry this energy more safely.
Resistance
But it isn’t reasonable to make all wire as thick as possible. First, price must be considered. If you increase the diameter of a wire, the amount of metal used will go up dramatically. For copper wire, this can mean a major increase in cost, let alone when using more expensive materials such as gold or silver. Therefore, when possible, using higher gauge (thinner) wire can be a much more effective use of resources. When running a small circuit with a small expected power drain, a thinner wire will work nearly as well, but be much cheaper than a heftier alternative. Conversely, when running a circuit to a large piece of industrial machinery with large power demands, a lower gauge will be necessary, both to ensure safe power transmission and to prevent power losses.
Material
Another thing which must be considered when deciding on wiring is what material to make the wire out of. Most metals are relatively ductile, which refers to their ability to stretch out when put under tension. This property allows them to be drawn out into wire. However, different metals have different other properties which make them more or less desirable for different circumstances. For example, copper has fairly low resistance, and is abundant enough that the costs are not too exorbitant for use as wiring. This makes it incredibly popular for use in many household and consumer electronics. Chances are, your household electrical system is nearly entirely made of copper wiring. The other quite common type of metal used in electrical systems is aluminum. While aluminum has higher resistance than copper, it is also much cheaper and lighter. Because it is so much cheaper and lighter, you can make it thicker to compensate for its increased resistance. In fact, an aluminum wire with equal resistance to a copper wire will be much lighter, even though it will also be much thicker. This makes it popular for use in situations where size is not a problem, but there might be large savings in cost or weight. For example, it is often used in overhead power lines.You can use quite thick wires on overhead lines without them getting in the way of anything, and the cheapness and lightness of aluminum make it ideal for this use.
There are a few other elements commonly used in wiring as well, although they are used much less frequently. Silver and gold are frequently used in electrical components, although their price limits their use. For example, gold resists oxidation, so can be incredibly useful in applications where electrical connection will need to be preserved despite exposure. Alternatively, sometimes high resistance is needed, and metals such as tungsten can be used.
Stranded or Solid
The final thing I will talk about here is the difference between stranded and single core wire. Stranded wire is made up of a large number of individual wires bundled together. Solid wire, on the other hand, has a single thick wire at its core. Solid wire has the advantage of durability and price. It is easier to manufacture, and uses a similar amount of raw material, so it will typically be cheaper. Additionally, it is less likely to suffer spontaneous failure if exposed to the elements or corrosion. However, it is also difficult to move. Stranded wire is much more useful in applications such as electronics with moving pieces, where it will be required to flex and bend regularly. The strands can slide against one another, decreasing the overall stress on the wire during this movement.