i know both of them are great conductors for electricity, but why is copper better and/or safer?
Aluminum Wire Vs Copper Wire
Copper is better than aluminum because it has a conductivity of 97% compared to 62 % for aluminum.Copper is also and safer, because, its contacts when splicing will remain conducting even for a long time, while in aluminum, splices specially if done copper to aluminum will oxidize after a period, resulting to overheating and electrical fires. Aluminum building wiring is not yet allowed in many Asian cities.
The crystalline structure of copper is more suited to distribute electrons between cells. This means lower resistance to the current flow which means less lost energy in the power lines. Flip side: Aluminum is better than copper because it is much cheaper and lighter weight. Aluminum is usually used in high voltage lines. From source 1: CHARACTERISTICS COPPER ALUMINUM Tensile strength (lb/in2).55,000 25,000 Tensile strength for same conductivity (lb). 55,000 40,000 Weight for same conductivity (lb). 100 48 Cross section for same conductivity (C.M.). 100 160 Specific resistance (W/mil ft). 10.6 17 Also, wires usually contain a lot of smaller strands due to skin effect (see the wiki page).
Aluminum and copper are both very good electrical conductors. Aluminum is less expensive and lighter in weight, and is preferred in higher voltage industrial/utility applications. But in residential applications, copper is preferred. The reason for this has to do with two metallurgical properties of aluminum. First, aluminum corrodes, and the corroded aluminum is an insulator. Unfortunately, aluminum corrodes very quickly, and the corrosion is not visibly obvious. As a result. corrosion can be present in a connection involving aluminum conductors, and this corrosion can lead to localized heating in the connection. The other problem is 'cold flow' - specifically, that when aluminum is placed under pressure, it will gradually conform to whatever physical constraint caused that pressure in a way that leads to a reduction in pressure. When connections are made to aluminum conductors, this characteristic causes those connections to gradually loosen over time as the aluminum 'flows' out of the joint. When aluminum is used in industrial or utility applications, special connectors are used that incorporate springs that maintain clamping pressure on the connection in spite of the tendency of the aluminum to 'flow'. In addition, a conductive grease, basically high-quality petroleum-based grease containing fine particles of zinc is use in the connection. The zinc particles pierce through the surface corrosion on the aluminum to assure that the connection is electrically sound. Unfortunately, these techniques aren't very practical in residential wiring applications. Hence. most building codes discourage the use of aluminum wiring in homes.
