You may know the metal copper best from older pennies, which are made of copper and other metals. But copper plays many crucial roles around the world due to its unique properties. One of these properties is its conductivity, or its ability to conduct electricity. Copper’s high conductivity makes it ideal for electrical purposes.
TL;DR (Too Long; Didn't Read)
Copper is a non-precious, red-gold colored metal with high electrical conductivity. In fact, the conductivity of copper is so high that it is considered the standard by which other non-precious metals and alloys are compared. The conductivity of copper is affected by the addition of other metals to make alloys.
Properties of Copper
Copper is an attractive red-gold colored metal. It is named copper after the Old English word “coper,” which originated from "Cyprium aes," which is the Latin word for a metal from Cyprus. Copper’s atomic symbol is “Cu,” and its atomic number is 29. Copper was the first metal humans ever worked. Eventually, people discovered that if they combined copper with the metal tin, they could make a new kind of metal called bronze. This launched what we call the Bronze Age, in which civilization leapt forward with the aid of the metal copper. Bronze was used in currency and tools that helped change society.
Copper is often found alongside sulfur. Important sources of copper include chalcopyrite and bornite. Copper is extracted from mined copper sulfide ore by smelting and then refining via electrolysis.
A useful property of copper is its ductility, or ability to be stretched. Copper can be pulled and twisted, yet it will not break. This makes it ideal for use as wire. Copper is a malleable metal, meaning it can easily be shaped and manipulated. As such, it is somewhat soft. Another property of copper is its excellent ability to conduct heat. Copper does not succumb to corrosion like some other metals, nor does it oxidize or rust like iron. Copper in fact is resistant to many organic compounds, and perhaps its most valuable property is its high conductivity.
Copper is an excellent metal for machining and jointing, as it is easy to shape and solder. Additionally, an excellent and valuable property of copper is its ability to be recycled. It does not matter whether a copper source is from a mine or from recycling materials. Its many helpful properties remain regardless of its source.
Alloys are mixtures of metals, such as the mixture of copper and tin to make bronze, which is a harder metal than copper. Metal alloys possess some of the same properties of their parent metals, but they can prove to be vastly different in behavior as well. Alloy mixtures can affect the electrical conductivity of metals, for example. The combination of various metals with copper results in unique traits for each alloy. When copper is combined with silver, the resulting alloy possesses many of the same features as pure copper. But if copper is combined with phosphorus, the resulting alloy behaves in a quite different manner.
Different copper alloys provide different uses. Quite often, alloys are made either to strengthen copper or increase its electrical-conductivity qualities.
Conductivity of Copper
The conductivity of metals refers to the ability of metals to conduct electricity. The conductivity can change with the addition of other metals, such as when making alloys. The metal with the greatest conductivity is the precious metal silver. Silver’s cost prevents it from being economically viable for broad-scale electrical uses. Among non-precious metals, copper or Cu conductivity is the highest. That means that copper can carry more electrical current than other non-precious metals. In fact, the conductivity of other non-precious metals is compared to copper because copper has become the ultimate standard.
The standard of conductivity is called the International Annealed Copper Standard, or IACS. The percentage of IACS of a substance refers to its electrical conductivity, and pure copper’s IACS percentage is considered 100 percent. In contrast, the conductivity of aluminum ranks at 61 percent IACS. Cu conductivity is affected by the addition of various metals to form alloys. Copper alloys with greater than 99.3 percent copper content are called “Coppers.” Some alloys contain very high percentages of copper, and those are called “High Copper Alloys.” While the percentage of copper affects Cu conductivity, it is most strikingly affected by what kind of materials it is combined with. A tradeoff generally occurs, when coppery alloys are made to be stronger. Generally these alloys are lower in conductivity.
Cu-ETP (Electronic Touch Pitch) has 100 percent IACS and is the designation for the kind of copper used in wires, cables and bus bars. Cast copper, or Cu-C, is 98 percent IACS, so it is also high in conductivity. When tin, magnesium, chromium, iron or zirconium is added to make alloys with copper, the metal’s strength rises, but its conductivity drops. For example, copper-tin or CuSnO.15 has a Cu conductivity as low as 64 percent IACS. Depending on the alloy function, the Cu conductivity can drop considerably. There are still alloys that provide both good machinability and high conductivity combined. Examples of his include copper-tellurium (CuTep) and copper-sulfur (CuSP) alloys. Their conductivities range from 64 to 98 percent IACS. These alloys prove to be quite useful for semiconductor mounts and resistance welding tips. Sometimes copper-based materials require high hardness and strength with moderate Cu conductivity; an example is a mixture of copper, nickel and silicon, which gives a Cu conductivity of 45 to 60 percent IACS. On the low-conductivity end of the scale, brasses are copper alloys that are excellent for casting. Their percentage of IACS hovers around 20. One example of these low Cu-conductivity alloys is copper-zinc. Sometimes a balanced alloy provides low to moderate Cu conductivity, which is useful for electrical needs. Copper-zinc brasses fall into this category, and their conductivity ranges from 28 to 56 percent IACS. The sheer versatility of copper and its ability to form useful alloys with so many different metals is incredible.
As Cu conductivity is so high, its ability to transmit heat is also quite high. Making copper alloys with high conductivity requires making alloys resistant to overheating when they carry electrical current. This is crucial in energy transmission, as higher heat will affect resistance.
Uses of Copper
Copper is used in many ways, both physically and biologically. It is also used in agriculture as a poison. Solutions of copper are commonly used as part of chemical tests. In the body, copper plays a role as an essential element that is necessary for energy transfer in cells. Some crustaceans even use copper instead of iron as their primary oxygen transporter.
Copper is of course used in making coins; older pennies are one example. In fact, most coins contain at least a little bit of copper in them.
Copper is mostly used in the transmission and delivery of electricity to all the everyday things you use. Copper is used extensively in electrical wiring, construction, machinery, telecommunication, power transmission, transportation and other industrial uses. It can be used for cables, transformers and connector parts. Copper is also used in computers and microcircuits.
As the sustainable energy market grows, so does the demand for copper. Copper is extremely useful in many areas and also able to be recycled over and over. Therefore it is a key component of renewable energy systems. In fact solar, wind and electric vehicle industries rely upon copper to connect them to the power grid. Electric vehicles require much more copper than gas-powered vehicles. Copper’s high conductivity makes it greatly efficient. It seems fitting that the oldest-used metal by humans will continue to offer benefits well into the future.
- European Copper Institute: Electrical Systems Depend on Copper’s Electrical Conductivity
- European Copper Institute: Introduction to the Copper Conductivity Materials Database
- Copper Development Association: Electrical and Thermal Conductivity
- Copper Development Association: Discussion of Conductivity
- Engineers Journal: Applications of High Conductivity Copper and Alloys for Electrical Engineering
- Royal Society of Chemistry: Periodic Table: Copper
- USGS Minerals Information: Copper Statistics and Information
About the Author
J. Dianne Dotson is a science writer with a degree in zoology/ecology and evolutionary biology. She spent nine years working in laboratory and clinical research. A lifelong writer, Dianne is also a content manager and science fiction & fantasy novelist. Dianne features science as well as writing topics on her website, jdiannedotson.com.