One of the major attributes of many metals is the ability to conduct electricity, and aluminum is one of the best performers in this application. As an electrical conductor, few materials can rival aluminum. That’s why so many industries and technologies, from high tech consumer devices to aerospace to heavy-duty transformers, have turned to aluminum alloys as a solution.
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The chemical composition of metal means that in most cases, the metallic bonding allows for the conduction of electricity. Metallic atoms are surrounded by constantly moving electrons that enable electricity to easily move among the ions. While aluminum is not the best metal conductor, it is only surpassed by pure silver (#1), pure copper (#2), and pure gold (#3). At the other end of the spectrum, iron is a middling conductor, while stainless steel is one of the worst.
Because of the obvious expense that would be involved, silver and gold are not viable options on an industrial scale. That leaves only copper as a more feasible conductor of electricity, and when you compare the two, aluminum has many advantages that make it more appealing to manufacturers and designers.
Today we’ll be examining the ways aluminum alloys are used in electrical devices and what you need to know when selecting a grade that is right for you.
Aluminum is naturally a conductor
First, aluminum on its own is one of the best metals for conducting electricity. Aluminum is actually capable of what is known as super conductivity, which is when the electrical resistance of a material vanishes and the magnetic flux fields are expelled. In a normal metallic conductor, the resistance will gradually decrease as it cools, while in a superconductor there is a critical temperature at which the resistance will suddenly drop to zero. This means that an ordinary electric current can persist indefinitely through a loop of superconducting wire without the need of a power source.
In aluminum, the superconducting critical temperature is 1.2 kelvin. Its critical magnetic field is approximately 100 gauss. Another attribute of aluminum is that it’s paramagnetic, so it does not need to worry about static magnetic fields. It should be noted however that it can be strongly impacted by a changing magnetic field as the result of the induction of eddy currents.
When compared to copper, aluminum exhibits just over half (61 percent to be exact) the conductivity of copper. On its face, this seems to suggest copper is the better option as a conductor, but that neglects the fact that aluminum is one-third the weight of copper. Therefore, if you have two metal wires, one copper, one aluminum, capable of conducting the same amount of electricity, the aluminum one will weigh half as much. Aluminum also tends to be less expensive for this reason.
What applications most commonly rely on aluminum as a conductor?
Aluminum is such a good conductor of electricity that even aluminum foil can be used as a conductor. Foil tends to be too delicate for most industrial applications, but it just goes to show the advantages of this material.
One of the most familiar and oldest applications for aluminum is electrical wire. Most of the insulated power cables in America’s electrical supply are made of aluminum, for the aforementioned weight and cost reasons. Copper cables would weigh much more than the aluminum ones, that’s why aluminum has been found in the nation’s power grid as far back as the late 1800’s.
Besides overhead power cables, aluminum wiring can also be found in some airplanes, homes, electronic devices and appliances such as fans, lamps and more.
With that in mind, in smaller wire sizes, copper will often be preferred to aluminum. This is because aluminum wiring does have one drawback that you should be aware of: it can be extremely corrosive when combined with other metals, meaning that you can’t use aluminum wire with copper conductors, as an example. Because copper was used in many of the first electrical devices, much of our infrastructure relies on copper. Switching over to aluminum would be prohibitively expensive, and that’s the reason why aluminum wiring was largely relegated to overhead power cables for many decades.
More recently, however, more and more copper wiring is being replaced by aluminum. This means that it’s important for you to do your research and understand how your application will be used and what the current wiring requirements (copper or aluminum) are.
What are aluminum electrical cables made of?
There are four main types of aluminum power cables. The first is known as All Aluminum Conductor (AAC) and consists of Electrical Conductor grade aluminum. This aluminum alloy is not very strong, and although its conductivity is 61% that of copper, it is not seen very often in transmission lines. You will find it in urban distribution lines, which tend to have shorter spans and higher requirements for conductivity.
Next is All Aluminum Alloy Conductor (AAAC), which is made from alloy 6201. This alloy offers excellent strength, with about 52% the conductivity of copper. It is frequently used for distribution and is especially useful in coastal areas because of its corrosion resistance.
Aluminum Conductor, Steel Reinforced (ACSR) combines a steel core with layers of aluminum 1350 alloy wires wrapped around it in spiral. With the significantly increased strength provided by the steel core, there is much less sag, making this kind of cable suitable for both transmission and distribution. You will often find it used in river crossings and other areas where higher strength is necessary.
Finally, Aluminum Conductor, Alloy Reinforced (ACAR) combines aluminum 1350 wrapped around a 6201 aluminum alloy core. This results in improved electrical and mechanical properties than ACSR, making it more reliable, though more expensive than other cables. It can be found in both overhead transmission and distribution lines.
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Your Technical Services Professional
At Clinton Aluminum, our goal is to be more than just an aluminum supplier. We strive to be true partners to our customers. This is especially important when dealing with complicated applications that involve electrical conductivity. We are committed to helping you through every step of your procurement process. Contact us today to get the help of sales professionals who have a deep understanding of the different types of aluminum alloys and the many benefits they provide.