There are different types of wiring, designed for both indoor and outdoor use as well as underground wiring. Some wires are resistant to heat as well as being corrosion proof. Wiring can be made from copper or aluminum and comes in many different sizes and ampacity carrying strengths. Read on to learn more.
Aluminum wiring was popular in the past though today copper is far more common as it offers better heat resistant properties. The reason for wires to be colored is to identify them for uses. For example green is always for grounding, no exceptions! Normally, the colors are normally black and white for two conductor wiring and red, black and white for three conductor wiring. In most cases, the black or black and red are used as hot wires for feeds or traveling conductors. The white is usually neutral, but not in all cases. You see, sometimes the third wire, being the white wire, is used as a “hot’ or “switch leg” in the circuit.
In these cases, you need to wrap the end of the wire with electrical tape to identify it as such. This will ensure that no one confuses it use and ties it into the neutral wires. Because just looking at wires is hard if not impossible to distinguish between the different sizes and types, wires have something special on its coating to tell us what the wiring really is.
To help you understand the correct choice, manufacturers have labeled the outer coating of the wire with types and gauges of wire. You see, the insulation covering the wire tells the story about the wire itself. Along with different sizes of wire, there are many types of wire used around the home. Knowing which type of wire to use is just as important as determining the proper gauge, amperage limit, and the maximum wattage load limit of the electrical wire you choose.
Source: https://www.thespruce.com/choosing-electrical-wire-gauge-amperage-3969938