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Copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
has been used in
electrical wiring Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...
since the invention of the
electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in ...
and the
telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...
in the 1820s. The invention of the
telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...
in 1876 created further demand for copper wire as an electrical conductor. Copper is the
electrical conductor In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gene ...
in many categories of electrical wiring.Pops, Horace, 2008, Processing of wire from antiquity to the future, Wire Journal International, June, pp 58-66 Copper wire is used in
power generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its stor ...
,
power transmission Power transmission is the movement of energy from its place of generation to a location where it is applied to perform useful work. Power is defined formally as units of energy per unit time. In SI units: :\text = \frac = \frac Since the develo ...
,
power distribution Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmissi ...
,
telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...
,
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
circuitry, and countless types of
electrical equipment Electric(al) devices are devices that functionally rely on electric energy ( AC or DC) to drive their core parts (electric motors, transformers, lighting, rechargeable batteries, control electronics). They can be contrasted with traditional m ...
. Copper and its alloys are also used to make
electrical contact An electrical contact is an electrical circuit component found in electrical switches, relays, connectors and circuit breakers. Each contact is a piece of electrically conductive material, typically metal. When a pair of contacts touch, they c ...
s.
Electrical wiring Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...
in buildings is the most important market for the copper industry. Roughly half of all copper mined is used to manufacture electrical wire and cable conductors.


Properties of copper


Electrical conductivity

Electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
is a measure of how well a material transports an
electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons res ...
. This is an essential property in electrical wiring systems. Copper has the highest electrical conductivity rating of all non-
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lu ...
s: the electrical resistivity of copper = 16.78 nΩ•m at 20 °C. The theory of metals in their solid state helps to explain the unusually high electrical conductivity of copper. In a copper
atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, a ...
, the outermost 4s energy zone, or
conduction band In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in ...
, is only half filled, so many
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...
s are able to carry
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...
. When an
electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field ...
is applied to a copper wire, the conduction of electrons accelerates towards the
electropositive Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...
end, thereby creating a current. These electrons encounter resistance to their passage by colliding with impurity atoms, vacancies, lattice ions, and imperfections. The average distance travelled between collisions, defined as the "
mean free path In physics, mean free path is the average distance over which a moving particle (such as an atom, a molecule, or a photon) travels before substantially changing its direction or energy (or, in a specific context, other properties), typically as ...
", is inversely proportional to the resistivity of the metal. What is unique about copper is its long mean free path (approximately 100 atomic spacings at room temperature). This mean free path increases rapidly as copper is chilled. Because of its superior conductivity, annealed copper became the international standard to which all other electrical conductors are compared. In 1913, the
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and ...
defined the conductivity of commercially pure copper in its International Annealed Copper Standard, as 100% IACS = 58.0 MS/m at 20 °C, decreasing by 0.393%/°C. Because commercial purity has improved over the last century, copper conductors used in building wire often slightly exceed the 100% IACS standard.Copper Building Wire Systems
, Copper Development Association, Inc.
The main grade of copper used for electrical applications is electrolytic-tough pitch (ETP) copper (CW004A or
ASTM ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
designation C11040). This copper is at least 99.90% pure and has an electrical conductivity of at least 101% IACS. ETP copper contains a small percentage of
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
(0.02 to 0.04%). If high conductivity copper needs to be
welded Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as braz ...
or brazed or used in a reducing atmosphere, then specially-pure
oxygen-free copper Oxygen-free copper (OFC) or oxygen-free high thermal conductivity (OFHC) copper is a group of wrought high-conductivity copper alloys that have been electrolytically refined to reduce the level of oxygen to 0.001% or below. Specification Ox ...
(CW008A or ASTM designation C10100) may be used; it is about 1% more conductive (i.e., achieves a minimum of 101% IACS).Copper Wire Tables; Circular of the Bureau of Standards; No. 31; S. W. Stratton, Director; U.S. Department of Commerce; 1914 Several electrically conductive metals are less dense than copper, but require larger cross sections to carry the same current and may not be usable when limited space is a major requirement.
Aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
has 61% of the conductivity of copper. The cross sectional area of an aluminium conductor must be 56% larger than copper for the same current carrying capability. The need to increase the thickness of aluminium wire restricts its use in many applications, such as in small motors and automobiles. However, in some applications such as aerial
electric power transmission Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This is d ...
cables, aluminium predominates, and copper is rarely used.
Silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
, a
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lu ...
, is the only metal with a higher electrical conductivity than copper. The electrical conductivity of silver is 106% of that of annealed copper on the IACS scale, and the electrical resistivity of silver = 15.9 nΩ•m at 20 °C. The high cost of silver combined with its low
tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials ...
limits its use to special applications, such as joint plating and sliding contact surfaces, and plating for the conductors in high-quality
coaxial cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...
s used at frequencies above 30 MHz


Tensile strength

Tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials ...
measures the force required to pull an object such as rope, wire, or a structural beam to the point where it breaks. The tensile strength of a material is the maximum amount of tensile stress it can take before breaking. Copper’s higher tensile strength (200–250 N/mm2 annealed) compared to aluminium (100 N/mm2 for typical conductor alloys) is another reason why copper is used extensively in the building industry. Copper’s high strength resists stretching, neck-down, creep, nicks and breaks, and thereby also prevents failures and service interruptions. Copper is much heavier than aluminum for conductors of equal current carrying capacity, so the high tensile strength is offset by its increased weight.


Ductility

Ductility Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile str ...
is a material's ability to deform under
tensile stress In continuum mechanics, stress is a physical quantity. It is a quantity that describes the magnitude of forces that cause deformation. Stress is defined as ''force per unit area''. When an object is pulled apart by a force it will cause elonga ...
. This is often characterized by the material's ability to be stretched into a
wire Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is co ...
. Ductility is especially important in
metalworking Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale ...
because materials that crack or break under stress cannot be hammered, rolled, or drawn (drawing is a process that uses tensile forces to stretch metal). Copper has a higher ductility than alternate metal conductors with the exception of gold and silver. Because of copper’s high ductility, it is easy to draw down to diameters with very close tolerances.


Strength and ductility combination

Usually, the stronger a metal is, the less pliable it is. This is not the case with copper. A unique combination of high strength and high ductility makes copper ideal for wiring systems. At junction boxes and at terminations, for example, copper can be bent, twisted, and pulled without stretching or breaking.


Creep resistance

Creep Creep, Creeps or CREEP may refer to: People * Creep, a creepy person Politics * Committee for the Re-Election of the President (CRP), mockingly abbreviated as CREEP, an fundraising organization for Richard Nixon's 1972 re-election campaign Art ...
is the gradual deformation of a material from constant expansions and contractions under “load, no-load” conditions. This process has adverse effects on electrical systems: terminations can become loose, causing connections to heat up or create dangerous arcing. Copper has excellent creep characteristics that minimizes loosening at connections. For other metal conductors that creep, extra maintenance is required to check terminals periodically and ensure that screws remain tightened to prevent arcing and overheating.


Corrosion resistance

Corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
is the unwanted breakdown and weakening of a material due to chemical reactions. Copper generally resists corrosion from moisture, humidity, industrial pollution, and other atmospheric influences. However, any corrosion oxides, chlorides, and sulfides that do form on copper are somewhat conductive. Under many application conditions copper is higher on the
galvanic series The galvanic series (or electropotential series) determines the nobility of metals and semi-metals. When two metals are submerged in an electrolyte, while also electrically connected by some external conductor, the less noble (base) will experience ...
than other common structural metals, meaning that copper wire is less likely to be corroded in wet conditions. However, any more anodic metals in contact with copper will be corroded since they will essentially be sacrificed to the copper.


Coefficient of thermal expansion

Metals and other solid materials expand upon heating and contract upon cooling. This is an undesirable occurrence in electrical systems. Copper has a low coefficient of
thermal expansion Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kin ...
for an electrical conducting material. Aluminium, an alternate common conductor, expands nearly one third more than copper under increasing temperatures. This higher degree of expansion, along with aluminium’s lower ductility, can cause electrical problems when bolted connections are improperly installed. By using proper hardware, such as spring pressure connections and cupped or split washers at the joint, it may be possible to create aluminium joints that compare in quality to copper joints.


Thermal conductivity

Thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
is the ability of a material to conduct heat. In electrical systems, high thermal conductivity is important for dissipating waste heat, particularly at terminations and connections. Copper has a 60% higher thermal conductivity rating than aluminium, so it is better able to reduce thermal hot spots in electrical wiring systems.Pops, Horace, 1995, Physical Metallurgy of Electrical Conductors, in Nonferrous Wire Handbook, Volume 3: Principles and Practice, The Wire Association International, pp. 7-22


Solderability

Soldering Soldering (; ) is a process in which two or more items are joined by melting and putting a filler metal ( solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not inv ...
is a process whereby two or more metals are joined together by a heating process. This is a desirable property in electrical systems. Copper is readily soldered to make durable connections when necessary.


Ease of installation

The strength, hardness, and flexibility of copper make it very easy to work with. Copper wiring can be installed simply and easily with no special tools, washers, pigtails, or joint compounds. Its flexibility makes it easy to join, while its hardness helps keep connections securely in place. It has good strength for pulling wire through tight places (“pull-through”), including conduits. It can be bent or twisted easily without breaking. It can be stripped and terminated during installation or service with far less danger of nicks or breaks. And it can be connected without the use of special lugs and fittings. The combination of all of these factors makes it easy for electricians to install copper wire.


Types


Solid and stranded

Solid wire consists of one strand of copper metal wire, bare or surrounded by an insulator. Single-strand copper conductors are typically used as magnet wire in motors and transformers. They are relatively rigid, do not bend easily, and are typically installed in permanent, infrequently handled, and low flex applications. Stranded wire has a group of copper wires braided or twisted together. Stranded wire is more flexible and easier to install than a large single-strand wire of the same cross section. Stranding improves wire life in applications with vibration. A particular cross-section of a stranded conductor gives it essentially the same resistance characteristics as a single-strand conductor, but with added flexibility.


Cable

A copper cable consists of two or more copper wires running side by side and bonded, twisted or braided together to form a single assembly. Electrical cables may be made more flexible by stranding the wires. Copper wires in a cable may be bare or they may be plated to reduce
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...
with a thin layer of another metal, most often tin but sometimes
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
or
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
. Plating may lengthen wire life and makes
soldering Soldering (; ) is a process in which two or more items are joined by melting and putting a filler metal ( solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not inv ...
easier.
Twisted pair Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted b ...
and
coaxial In geometry, coaxial means that several three-dimensional linear or planar forms share a common axis. The two-dimensional analog is ''concentric''. Common examples: A coaxial cable is a three-dimensional linear structure. It has a wire condu ...
cables are designed to inhibit electromagnetic interference, prevent radiation of signals, and to provide
transmission line In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmi ...
s with defined characteristics. Shielded cables are encased in foil or wire mesh.


Applications

Electrolytic-tough pitch (ETP) copper, a high-purity copper that contains
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
as an
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...
ing agent, represents the bulk of
electrical conductor In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gene ...
applications because of its high
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
and improved annealability. ETP copper is used for
power transmission Power transmission is the movement of energy from its place of generation to a location where it is applied to perform useful work. Power is defined formally as units of energy per unit time. In SI units: :\text = \frac = \frac Since the develo ...
,
power distribution Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmissi ...
, and
telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...
. Common applications include building wire, motor windings,
electrical cable An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current. One or more electrical cables and their corresponding connectors may be formed into a ''cable assembly'', whic ...
s, and
busbar In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution. They are also used to connect high volt ...
s.
Oxygen-free copper Oxygen-free copper (OFC) or oxygen-free high thermal conductivity (OFHC) copper is a group of wrought high-conductivity copper alloys that have been electrolytically refined to reduce the level of oxygen to 0.001% or below. Specification Ox ...
s are used to resist
hydrogen embrittlement Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals. Once absorbe ...
when extensive amounts of
cold work Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute thermodynamic ...
is needed, and for applications requiring higher
ductility Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile str ...
(e.g., telecommunications cable). When hydrogen embrittlement is a concern and low electrical resistivity is not required,
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...
may be added to copper. For certain applications, copper alloy conductors are preferred instead of pure copper, especially when higher strengths or improved abrasion and
corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
resistance properties are required. However, relative to pure copper, the higher strength and corrosion resistance benefits that are offered by copper alloys are offset by their lower electrical conductivities. Design engineers weigh the advantages and disadvantages of the various types of copper and copper alloy conductors when determining which type to specify for a specific electrical application. An example of a copper alloy conductor is
cadmium Cadmium is a chemical element with the Symbol (chemistry), symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Li ...
copper wire, which is used for
railroad Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a prep ...
electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. The broad meaning of the term, such as in the history of technology, economic histo ...
in North America. In Britain the BPO (later
Post Office Telecommunications Post Office Telecommunications was set up as a separate department of the UK Post Office, in October 1969. The Post Office Act 1969 was passed to provide for greater efficiency in post and telephone services; rather than run a range of services, ...
) used cadmium copper aerial lines with 1% cadmium for extra strength; for local lines 40 lb/mile (1.3 mm dia) and for toll lines 70 lb/mile (1.7 mm dia). Some of the major application markets for copper conductors are summarized below.


Electrical wiring

Electrical wiring distributes electric power inside residential, commercial, or industrial buildings, mobile homes, recreational vehicles, boats, and substations at
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
s up to 600 V. The thickness of the wire is based on
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...
requirements in conjunction with safe operating temperatures. Solid wire is used for smaller diameters; thicker diameters are stranded to provide flexibility. Conductor types include non-metallic/non-metallic corrosion-resistant cable (two or more insulated conductors with a nonmetallic outer sheath), armored or BX cable (cables are surrounded by a flexible metal enclosure), metal clad cable, service entrance cable, underground feeder cable, TC cable, fire resistant cable, and mineral insulated cable, including mineral-insulated copper-clad cable. Copper is commonly used for building wire because of its conductivity, strength, and reliability. Over the life of a building wire system, copper can also be the most economical conductor. Copper used in building wire has a conductivity rating of 100% IACS or better. Copper building wire requires less insulation and can be installed in smaller conduits than when lower-conductivity conductors are used. Also, comparatively, more copper wire can fit in a given conduit than conductors with lower conductivities. This greater “wire fill” is a special advantage when a system is rewired or expanded. Copper building wire is compatible with brass and quality plated screws. The wire provides connections that will not corrode or creep. It is not, however, compatible with aluminium wire or connectors. If the two metals are joined, a galvanic reaction can occur. Anodic
corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
during the reaction can disintegrate the aluminium. This is why most appliance and electrical equipment manufacturers use copper lead wires for connections to building wiring systems. "All-copper" building wiring refers to buildings in which the inside electrical service is carried exclusively over copper wiring. In all-copper homes, copper conductors are used in
circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the ris ...
panels,
branch circuit Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...
wiring (to outlets, switches, lighting fixtures and the like), and in dedicated branches serving heavy-load appliances (such as ranges, ovens, clothes dryers and air conditioners). Attempts to replace copper with aluminium in building wire were curtailed in most countries when it was found that aluminium connections gradually loosened due to their inherent slow creep, combined with the high resistivity and heat generation of aluminium oxidation at joints. Spring-loaded contacts have largely alleviated this problem with aluminium conductors in building wire, but some building codes still forbid the use of aluminium. For branch-circuit sizes, virtually all basic wiring for lights, outlets and switches is made from copper. The market for aluminium building wire today is mostly confined to larger gauge sizes used in supply circuits. Electrical wiring codes give the allowable current rating for standard sizes of conductors. The current rating of a conductor varies depending on the size, allowable maximum temperature, and the operating environment of the conductor. Conductors used in areas where cool air is free to circulate around the wires are generally permitted to carry more current than the small sized conductor encased in an underground conduit run with many similar conductors adjacent to it. The practical temperature ratings of insulated copper conductors are mostly due to the limitations of the insulation material or of the temperature rating of the attached equipment.


Communications wiring


Twisted pair cable

Twisted pair Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted b ...
cabling is the most popular network cable and is often used in
data network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are m ...
s for short and medium length connections (up to 100 meters or 328 feet). This is due to its relatively lower costs compared to optical fiber and coaxial cable. Unshielded twisted pair (UTP) cables are the primary cable type for telephone usage. In the late 20th century, UTPs emerged as the most common cable in computer networking cables, especially as
patch cable A patch cable, patch cord or patch lead is an electrical or optical cable used to connect ("patch in") one electronic or optical device to another for signal routing. Devices of different types (e.g., a switch connected to a computer, or a s ...
s or temporary network connections. They are increasingly used in video applications, primarily in security cameras. UTP plenum cables that run above ceilings and inside walls use a solid copper core for each conductor, which enables the cable to hold its shape when bent. Patch cables, which connect computers to wall plates, use stranded copper wire because they are expected to be flexed during their lifetimes. UTPs are the best balanced line wires available. However they are the easiest to tap into. When interference and security are concerns, shielded cable or
fiber optic cable A fiber-optic cable, also known as an optical-fiber cable, is an assembly similar to an electrical cable, but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with ...
is often considered. UTP cables include:
Category 3 cable Category 3 cable, commonly known as or station wire, and less commonly known as VG or voice-grade (as, for example, in 100BaseVG), is an unshielded twisted pair (UTP) cable used in telephone wiring. It is part of a family of standards defin ...
, now the minimum requirement by the FCC (USA) for every telephone connection; Category 5e cable, 100-MHz enhanced pairs for running Gigabit Ethernet (1000Base-T); and
Category 6 cable Category 6 cable (Cat 6) is a standardized twisted pair cable for Ethernet and other network physical layers that is backward compatible with the Category 5/5e and Category 3 cable standards. Cat 6 must meet more stringent ...
, where each pair runs 250 MHz for improved 1000Base-T performance. In copper twisted pair wire networks,
copper cable certification In copper twisted pair wire networks, copper cable certification is achieved through a thorough series of tests in accordance with Telecommunications Industry Association (TIA) or International Organization for Standardization (ISO) standards. T ...
is achieved through a thorough series of tests in accordance with
Telecommunications Industry Association The Telecommunications Industry Association (TIA) is accredited by the American National Standards Institute (ANSI) to develop voluntary, consensus-based industry standards for a wide variety of Information and Communication Technologies ( ICT) ...
(TIA) or
International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in A ...
(ISO) standards.


Coaxial cable

Coaxial cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...
s were extensively used in
mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...
systems and were the first type of major cable used for Local Area Networks (
LAN Lan or LAN may also refer to: Science and technology * Local asymptotic normality, a fundamental property of regular models in statistics * Longitude of the ascending node, one of the orbital elements used to specify the orbit of an object in spa ...
). Common applications for coaxial cable today include computer network (Internet) and instrumentation data connections, video and CATV distribution, RF and microwave transmission, and feedlines connecting
radio transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
s and receivers with their antennas. While coaxial cables can go longer distances and have better protection from EMI than twisted pairs, coaxial cables are harder to work with and more difficult to run from offices to the wiring closet. For these reasons, it is now generally being replaced with less expensive UTP cables or by
fiber optic cable A fiber-optic cable, also known as an optical-fiber cable, is an assembly similar to an electrical cable, but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with ...
s for more capacity. Today, many CATV companies still use coaxial cables into homes. These cables, however, are increasingly connected to a fiber optic data communications system outside of the home. Most building management systems use proprietary copper cabling, as do paging/audio speaker systems. Security monitoring and entry systems still often depend on copper, although fiber cables are also used.


Structured wiring

Most
telephone line A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or ot ...
s can share voice and data simultaneously. Pre-digital quad telephone wiring in homes is unable to handle communications needs for multiple phone lines, Internet service, video communications, data transmission, fax machines, and security services.
Crosstalk In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, i ...
, static interference, inaudible signals, and interrupted service are common problems with outdated wiring. Computers connected to old-fashioned communications wiring often experience poor Internet performance. “ Structured wiring” is the general term for 21st century
On-premises wiring On-premises wiring (customer premises wiring) is customer-owned telecommunication transmission or distribution lines. The transmission lines may be metallic (copper) or optical fiber, and may be installed within or between buildings. Premises ...
for high-capacity telephone, video, data-transmission, security, control, and entertainment systems. Installations usually include a central distribution panel where all connections are made, as well as outlets with dedicated connections for phone, data, TV and audio jacks. Structured wiring enables computers to communicate with each other error-free and at high speeds while resisting interference among various electrical sources, such as household appliances and external communications signals. Networked computers are able to share high-speed Internet connections simultaneously. Structured wiring can also connect computers with printers, scanners,
telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...
s, fax machines, and even home security systems and home entertainment equipment. Quad-shielded
RG-6 RG-6/U is a common type of coaxial cable used in a wide variety of residential and commercial applications. An RG-6/U coaxial cable has a characteristic impedance of 75 ohms. The term, ''RG-6'', is generic and is applied to a wide variety of ...
coaxial cable can carry a large number of TV channels at the same time. A star wiring pattern, where the wiring to each jack extends to a central distribution device, facilitates flexibility of services, problem identification, and better signal quality. This pattern has advantages to daisy chain loops. Installation tools, tips, and techniques for networked wiring systems using twisted pairs, coaxial cables, and connectors for each are available. Structured wiring competes with wireless systems in homes. While wireless systems certainly have convenience advantages, they also have drawbacks over copper-wired systems: the higher bandwidth of systems using Category 5e wiring typically support more than ten times the speeds of wireless systems for faster data applications and more channels for video applications. Alternatively, wireless systems are a security risk as they can transmit sensitive information to unintended users over similar receiver devices. Wireless systems are more susceptible to interference from other devices and systems, which can compromise performance. Certain geographic areas and some buildings may be unsuitable for wireless installations, just as some buildings may present difficulties installing wires.


Power distribution

Power distribution Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmissi ...
is the final stage in the delivery of electricity for an end use. A power distribution system carries electricity from the transmission system to consumers. Power cables are used for the transmission and distribution of electric power, either outdoors or inside buildings. Details on the various types of power cables are available.Electric Wire and Cable, brochure 0001240, Cobre Cerrillos S.A., Santiago, Chile; Cocessa Technical Bulletin, Electrical Conductor Catalog 751, MADECO, 1990 Copper is the preferred conductor material for underground transmission lines operating at high and extra-high voltages to 400 kV. The predominance of copper underground systems stems from its higher volumetric electrical and thermal conductivities compared to other conductors. These beneficial properties for copper conductors conserve space, minimize power loss, and maintain lower cable temperatures. Copper continues to dominate low-voltage lines in mines and underwater applications, as well as in electric railroads, hoists, and other outdoor services.Joseph, Günter, 1999, Copper: Its Trade, Manufacture, Use, and Environmental Status, edited by Kundig, Konrad J.A., ASM International Vol. 2.03, Electrical Conductors Aluminium, either alone or reinforced with steel, is the preferred conductor for overhead transmission lines due to its lighter weight and lower cost.


Appliance conductors

Appliance conductors for domestic applications and instruments are manufactured from bunch-stranded soft wire, which may be tinned for soldering or phase identification. Depending upon loads, insulation can be PVC, neoprene, ethylene propylene, polypropylene filler, or cotton.


Automotive conductors

Automotive conductors require insulation that is resistant to elevated temperatures, petroleum products, humidity, fire, and chemicals. PVC, neoprene, and polyethylene are the most common insulators. Potentials range from 12 V for electrical systems to between 300 V - 15,000 V for instruments, lighting, and ignition systems.


Magnet wire

Magnet wire Magnet wire or enameled wire is a copper (Cu) or aluminium (Al) wire coated with a very thin layer of insulation. It is used in the construction of transformers, inductors, motors, generators, speakers, hard disk head actuators, elect ...
or winding wire is used in windings of
electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate f ...
s,
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s,
inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
s, generators,
headphone Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an a ...
s,
loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
coils, hard drive head positioners,
electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in ...
s, and other devices. Most often, magnetic wire is composed of fully annealed, electrolytically refined copper to allow closer winding when making electromagnetic coils. The wire is coated with a range of
polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
ic insulations, including
varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in variou ...
, rather than the thicker plastic or other types of insulation commonly used on electrical wire. High-purity
oxygen-free copper Oxygen-free copper (OFC) or oxygen-free high thermal conductivity (OFHC) copper is a group of wrought high-conductivity copper alloys that have been electrolytically refined to reduce the level of oxygen to 0.001% or below. Specification Ox ...
grades are used for high-temperature applications in reducing atmospheres or in motors or generators cooled by hydrogen gas.


Splice closures for copper cables

A copper splice closure is defined as an enclosure, and the associated hardware, that is intended to restore the mechanical and environmental integrity of one or more copper cables entering the enclosure and providing some internal function for splicing, termination, or interconnection.


Types of closures

As stated in
Telcordia iconectiv is a supplier of network planning and network management services to telecommunications providers. Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name ...
industry requirements documen
GR-3151
there are two principal configurations for closures: butt closures and in-line closures. Butt closures permit cables to enter the closure from one end only. This design may also be referred to as a dome closure. These closures can be used in a variety of applications, including branch splicing. In-line closures provide for the entry of cables at both ends of the closure. They can be used in a variety of applications, including branch splicing and cable access. In-line closures can also be used in a butt configuration by restricting cable access to one end of the closure. A copper splice closure is defined by the functional design characteristics and, for the most part, is independent of specific deployment environments or applications. At this time,
Telcordia iconectiv is a supplier of network planning and network management services to telecommunications providers. Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name ...
has identified two types of copper closures: # Environmentally Sealed Closures (ESCs) # Free-Breathing Closures (FBCs) ESCs provide all of the features and functions expected of a typical splice closure in an enclosure that prevents the intrusion of liquid and vapor into the closure interior. This is accomplished through the use of an environmental sealing system such as rubber gaskets or hot-melt adhesives. Some ESCs use pressurized air to help keep moisture out of the closure. FBCs provide all of the features and functions expected of a typical splice closure that prevents the intrusion of wind-driven rain, dust, and insects. Such a closure, however, permits the free exchange of air with the outside environment. Therefore, it is possible that condensation will form inside the closure. It is thus necessary to provide adequate drainage to prevent the accumulation of water inside the closure.


Future trends

Copper will continue to be the predominant material in most electrical wire applications, especially where space considerations are important. The automotive industry for decades has considered the use of smaller-diameter wires in certain applications. Many manufacturers are beginning to use copper alloys such as copper-magnesium (CuMg), which allow for smaller diameter wires with less weight and improved conductivity performance. Special alloys like copper-magnesium are beginning to see increased usage in automotive, aerospace, and defense applications. Due to the need to increase the transmission of high-speed voice and data signals, the surface quality of copper wire is expected to continue to improve. Demands for better drawability and movement towards “zero” defects in copper conductors are expected to continue. A minimum mechanical strength requirement for magnet wire may evolve in order to improve formability and prevent excessive stretching of wire during high speed coiling operations. It does not seem likely that standards for copper wire purity will increase beyond the current minimum value of 101% IACS. Although 6-nines copper (99.9999% pure) has been produced in small quantities, it is extremely expensive and probably unnecessary for most commercial applications such as magnet, telecommunications, and building wire. The electrical conductivity of 6-nines copper and 4-nines copper (99.99% pure) is nearly the same at ambient temperature, although the higher-purity copper has a higher conductivity at cryogenic temperatures. Therefore, for non-cryogenic temperatures, 4-nines copper will probably remain the dominant material for most commercial wire applications.


Theft

During the 2000s commodities boom, copper prices increased worldwide, increasing the incentive for criminals to steal copper from power supply and communications cables.


See also

*
Magnet wire Magnet wire or enameled wire is a copper (Cu) or aluminium (Al) wire coated with a very thin layer of insulation. It is used in the construction of transformers, inductors, motors, generators, speakers, hard disk head actuators, elect ...
*
Annealing by short circuit Annealing by short circuit is a method of efficiently annealing copper wire which employs a controlled electrical short circuit. It can be advantageous because it does not require a temperature-regulated furnace like other methods of annealing. ...
*
Copper cable certification In copper twisted pair wire networks, copper cable certification is achieved through a thorough series of tests in accordance with Telecommunications Industry Association (TIA) or International Organization for Standardization (ISO) standards. T ...
* Copper sulfide *
Copper-clad aluminium wire Copper-clad aluminium wire (CCAW or CCA) is a dual metal electrical conductor composed of an inner aluminium core and outer copper cladding. Uses The primary applications of this conductor revolve around weight reduction requirements. These a ...
* Copper-clad steel *
Galvanization Galvanization or galvanizing ( also spelled galvanisation or galvanising) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerge ...
* Mineral-insulated copper-clad cable *
Passivation (chemistry) Passivation, in physical chemistry and engineering, refers to coating a material so it becomes "passive", that is, less readily affected or corroded by the environment. Passivation involves creation of an outer layer of shield material that is a ...
* Solderability


References

{{Reflist, 2 Copper Electrical wiring Power cables