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121-402: 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 wire and cable types and sizes are specified according to the circuit operating voltage and electric current capability, with further restrictions on

242-514: A brass or lead-coated iron sheet tube, with a crimped seam. The enclosure could also be used as a return conductor. Kuhlo wire could be run exposed on surfaces and painted, or embedded in plaster. Special outlet and junction boxes were made for lamps and switches, made either of porcelain or sheet steel. The crimped seam was not considered as watertight as the Stannos wire used in England, which had

363-514: A cable is permitted to carry. Because multiple conductors bundled in a cable cannot dissipate heat as easily as single insulated conductors, those circuits are always rated at a lower ampacity . Tables in electrical safety codes give the maximum allowable current based on size of conductor, voltage potential, insulation type and thickness, and the temperature rating of the cable itself. The allowable current will also be different for wet or dry locations, for hot (attic) or cool (underground) locations. In

484-456: A commutator. The molding plate is also fabricated into tubes and rings for insulation in armatures, motor starters , and transformers. Segment plate acts as insulation between the copper commutator segments of direct-current universal motors and generators. Phlogopite built-up mica is preferred because it wears at the same rate as the copper segments. Although muscovite has a greater resistance to wear, it causes uneven ridges that may interfere with

605-410: A copper tube and the space filled with magnesium oxide powder. The whole assembly is drawn down to smaller sizes, thereby compressing the powder. Such cables have a certified fire resistance rating and are more costly than non–fire-rated cable. They have little flexibility and behave more like rigid conduit rather than flexible cables. The environment of the installed wires determine how much current

726-686: A flexible plastic jacket. In North America and the UK this conductor is usually bare wire but in the UK it is required that this bare Protective Earth (PE) conductor be sheathed in Green/Yellow insulating tubing where the Cable Sheathing has been removed. Most other jurisdictions now require the Protective Earth conductor to be insulated to the same standard as the current carrying conductors with Green/Yellow insulation. With some cables

847-584: A grooved punch and a grooved metal anvil . Swaging is of great antiquity, possibly dating to the beginning of the 2nd millennium BCE in Egypt and in the Bronze and Iron Ages in Europe for torcs and fibulae . Twisted square-section wires are a very common filigree decoration in early Etruscan jewelry. In about the middle of the 2nd millennium BCE, a new category of decorative tube was introduced which imitated

968-411: A grounded barrier from the adjacent phases (segregated bus). For conducting large currents between devices, a cable bus is used. For very large currents in generating stations or substations, where it is difficult to provide circuit protection, an isolated-phase bus is used. Each phase of the circuit is run in a separate grounded metal enclosure. The only fault possible is a phase-to-ground fault, since

1089-568: A line of granules. True beaded wire, produced by mechanically distorting a round-section wire, appeared in the Eastern Mediterranean and Italy in the seventh century BCE, perhaps disseminated by the Phoenicians . Beaded wire continued to be used in jewellery into modern times, although it largely fell out of favour in about the tenth century CE when two drawn round wires, twisted together to form what are termed 'ropes', provided

1210-440: A machine may have six bobbins on one cage and twelve on the other. Solid wire, also called solid-core or single-strand wire, consists of one piece of metal wire. Solid wire is useful for wiring breadboards. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire. Solid wire also provides mechanical ruggedness; and, because it has relatively less surface area which

1331-401: A mica disc and contained in a borosilicate glass gas discharge tube (arc tube) and a metal cap. They include the sodium-vapor lamp that is the gas-discharge lamp in street lighting. Another use of mica is as a substrate in the production of ultra-flat, thin-film surfaces, e.g. gold surfaces. Although the deposited film surface is still rough due to deposition kinetics, the back side of

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1452-442: A mild abrasive to aid the polishing of the tooth surface and also adds a cosmetically pleasing, glittery shimmer to the paste. Mica is added to latex balloons to provide a colored shiny surface. Muscovite and phlogopite splittings can be fabricated into various built-up mica products, also known as micanite . Produced by mechanized or hand setting of overlapping splittings and alternate layers of binders and splittings, built-up mica

1573-434: A quantifiable impact upon the ampacity derating, because the thermal insulation properties needed for fire resistance also inhibit air cooling of power conductors. Cable trays are used in industrial areas where many insulated cables are run together. Individual cables can exit the tray at any point, simplifying the wiring installation and reducing the labour cost for installing new cables. Power cables may have fittings in

1694-535: A reflective color depending on the thickness of the coating. These products are used to produce automobile paint, shimmery plastic containers, and high-quality inks used in advertising and security applications. In the cosmetics industry, its reflective and refractive properties make mica an important ingredient in blushes , eye liner , eye shadow , foundation , hair and body glitter, lipstick , lip gloss , mascara , moisturizing lotions, and nail polish. Some brands of toothpaste include powdered white mica. This acts as

1815-490: A run of cable through several areas, the part with the lowest rating becomes the rating of the overall run. Cables usually are secured with special fittings where they enter electrical apparatus; this may be a simple screw clamp for jacketed cables in a dry location, or a polymer-gasketed cable connector that mechanically engages the armour of an armoured cable and provides a water-resistant connection. Special cable fittings may be applied to prevent explosive gases from flowing in

1936-755: A second deposit was located in the Xalla Complex, another palatial structure east of Street of the Dead. There is a claim mica was found within the Pyramid of the Sun, which originates from Peter Tompkins in his book Mysteries of the Mexican Pyramids . But it is not yet proven. Natural mica was and still is used by the Taos and Picuris Pueblos Indians in north-central New Mexico to make pottery. The pottery

2057-527: A simpler-to-make alternative. A forerunner to beaded wire may be the notched strips and wires which first occur from around 2000 BCE in Anatolia . Wire was drawn in England from the medieval period. The wire was used to make wool cards and pins, manufactured goods whose import was prohibited by Edward IV in 1463. The first wire mill in Great Britain was established at Tintern in about 1568 by

2178-672: A single family home or duplex, for example, are simple, with relatively low power requirements, infrequent changes to the building structure and layout, usually with dry, moderate temperature and non-corrosive environmental conditions. In a light commercial environment, more frequent wiring changes can be expected, large apparatus may be installed and special conditions of heat or moisture may apply. Heavy industries have more demanding wiring requirements, such as very large currents and higher voltages, frequent changes of equipment layout, corrosive, or wet or explosive atmospheres. In facilities that handle flammable gases or liquids, special rules may govern

2299-488: A soldered sheath. A somewhat similar system called "concentric wiring" was introduced in the United States around 1905. In this system, an insulated electrical wire was wrapped with copper tape which was then soldered, forming the grounded (return) conductor of the wiring system. The bare metal sheath, at earth potential, was considered safe to touch. While companies such as General Electric manufactured fittings for

2420-432: A solid wire of the same diameter because the cross-section of the stranded wire is not all copper; there are unavoidable gaps between the strands (this is the circle packing problem for circles within a circle ). A stranded wire with the same cross-section of conductor as a solid wire is said to have the same equivalent gauge and is always a larger diameter. However, for many high-frequency applications, proximity effect

2541-434: A strong negative charge since their bulk composition is AlSi 3 O 10 . The octahedral sheet has a positive charge, since its bulk composition is Al(OH) (for a dioctahedral sheet with the apical sites vacant) or M 3 (OH) 2 (for a trioctahedral site with the apical sites vacant; M represents a divalent ion such as ferrous iron or magnesium) The combined TOT layer has a residual negative charge, since its bulk composition

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2662-439: Is birefringent and is therefore commonly used to make quarter and half wave plates . Specialized applications for sheet mica are found in aerospace components in air-, ground-, and sea-launched missile systems, laser devices, medical electronics and radar systems. Mica is mechanically stable in micrometer-thin sheets which are relatively transparent to radiation (such as alpha particles ) while being impervious to most gases. It

2783-490: Is Al 2 (AlSi 3 O 10 )(OH) 2 or M 3 (AlSi 3 O 10 )(OH) 2 . The remaining negative charge of the TOT layer is neutralized by the interlayer cations (typically sodium, potassium, or calcium ions). Because the hexagons in the T and O sheets are slightly different in size, the sheets are slightly distorted when they bond into a TOT layer. This breaks the hexagonal symmetry and reduces it to monoclinic symmetry. However,

2904-401: Is a 2/0 wire made from 5,292 strands of No. 36 gauge wire. The strands are organized by first creating a bundle of 7 strands. Then 7 of these bundles are put together into super bundles. Finally 108 super bundles are used to make the final cable. Each group of wires is wound in a helix so that when the wire is flexed, the part of a bundle that is stretched moves around the helix to a part that

3025-493: Is accomplished through the use of thicker, specially constructed jackets, and by tinning the individual wire stands. In North American practice, for residential and light commercial buildings fed with a single-phase split 120/240 service , an overhead cable from a transformer on a power pole is run to the service entrance point. The cable is a three conductor twisted "triplex" cable with a bare neutral and two insulated conductors, with no overall cable jacket. The neutral conductor

3146-457: Is composed of parallel TOT layers weakly bonded to each other by cations ( c ). The TOT layers in turn consist of two tetrahedral sheets ( T ) strongly bonded to the two faces of a single octahedral sheet ( O ). The relatively weak ionic bonding between TOT layers gives mica its perfect basal cleavage. The tetrahedral sheets consist of silica tetrahedra, each silicon ion surrounded by four oxygen ions. In most micas, one in four silicon ions

3267-494: Is compressed to allow the wire to have less stress. Prefused wire is stranded wire made up of strands that are heavily tinned , then fused together. Prefused wire has many of the properties of solid wire, except it is less likely to break. A braided wire consists of a number of small strands of wire braided together. Braided wires do not break easily when flexed. Braided wires are often suitable as an electromagnetic shield in noise-reduction cables. Wire has many uses. It forms

3388-441: Is considerably less abundant than flake and scrap mica, and is occasionally recovered from mining scrap and flake mica. The most important sources of sheet mica are pegmatite deposits. Sheet mica prices vary with grade and can range from less than $ 1 per kilogram for low-quality mica to more than $ 2,000 per kilogram for the highest quality. In Madagascar and India, it is also mined artisanally , in poor working conditions and with

3509-565: Is derived from the Latin word mica , meaning a crumb , and probably influenced by micare , to glitter. Human use of mica dates back to prehistoric times. Mica was known to ancient Indian , Egyptian , Greek , Roman , and Chinese civilizations, as well as the Aztec civilization of the New World . The earliest use of mica has been found in cave paintings created during

3630-453: Is exposed to attack by corrosives, protection against the environment. Stranded wire is composed of a number of small wires bundled or wrapped together to form a larger conductor. Stranded wire is more flexible than solid wire of the same total cross-sectional area. Stranded wire is used when higher resistance to metal fatigue is required. Such situations include connections between circuit boards in multi-printed-circuit-board devices, where

3751-408: Is in no less demand for fencing, and much is consumed in the construction of suspension bridges , and cages, etc. In the manufacture of stringed musical instruments and scientific instruments, wire is again largely used. Carbon and stainless spring steel wire have significant applications in engineered springs for critical automotive or industrial manufactured parts/components. Pin and hairpin making;

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3872-537: Is made from weathered Precambrian mica schist and has flecks of mica throughout the vessels. Tewa Pueblo Pottery is made by coating the clay with mica to provide a dense, glittery micaceous finish over the entire object. Mica flakes (called abrak in Urdu and written as ابرک ) are also used in Pakistan to embellish women's summer clothes, especially dupattas (long light-weight scarves, often colorful and matching

3993-485: Is more severe than skin effect, and in some limited cases, simple stranded wire can reduce proximity effect. For better performance at high frequencies, litz wire , which has the individual strands insulated and twisted in special patterns, may be used. The more individual wire strands in a wire bundle, the more flexible, kink-resistant, break-resistant, and stronger the wire becomes. However, more strands increases manufacturing complexity and cost. For geometrical reasons ,

4114-620: Is nowadays done by passing them through an extruder. Formerly, materials used for insulation included treated cloth or paper and various oil-based products. Since the mid-1960s, plastic and polymers exhibiting properties similar to rubber have predominated. Two or more wires may be wrapped concentrically, separated by insulation, to form coaxial cable . The wire or cable may be further protected with substances like paraffin , some kind of preservative compound, bitumen, lead , aluminum sheathing, or steel taping. Stranding or covering machines wind material onto wire which passes through quickly. Some of

4235-496: Is often a supporting "messenger" steel wire, which is used to support the insulated line conductors. Electrical devices often use copper conductors because of their properties, including their high electrical conductivity , tensile strength , ductility , creep resistance, corrosion resistance , thermal conductivity , coefficient of thermal expansion , solderability , resistance to electrical overloads , compatibility with electrical insulators , and ease of installation. Copper

4356-585: Is only from these and certain of their alloys with other metals, principally brass and bronze , that wire is prepared. By careful treatment, extremely thin wire can be produced. Special purpose wire is however made from other metals (e.g. tungsten wire for light bulb and vacuum tube filaments, because of its high melting temperature). Copper wires are also plated with other metals, such as tin, nickel, and silver to handle different temperatures, provide lubrication, and provide easier stripping of rubber insulation from copper. Metallic wires are often used for

4477-489: Is permitted, unless the fitting is rated or listed for multiple cables. Special cable constructions and termination techniques are required for cables installed in ships. Such assemblies are subjected to environmental and mechanical extremes. Therefore, in addition to electrical and fire safety concerns, such cables may also be required to be pressure-resistant where they penetrate a vessel's bulkheads. They must also resist corrosion caused by salt water or salt spray , which

4598-400: Is replaced by an aluminium ion, while aluminium ions replace half the silicon ions in brittle micas. The tetrahedra share three of their four oxygen ions with neighbouring tetrahedra to produce a hexagonal sheet. The remaining oxygen ion (the apical oxygen ion) is available to bond with the octahedral sheet. The octahedral sheet can be dioctahedral or trioctahedral. A trioctahedral sheet has

4719-477: Is resistant to corona discharge . Muscovite, the principal mica used by the electrical industry, is used in capacitors that are ideal for high frequency and radio frequency. Phlogopite mica remains stable at higher temperatures (to 900 °C (1,650 °F)) and is used in applications in which a combination of high-heat stability and electrical properties is required. Muscovite and phlogopite are used in sheet and ground forms. The leading use of dry-ground mica in

4840-798: Is solid wire, since the wiring is not required to be very flexible. Building wire conductors larger than 10 AWG (or about 5 mm) are stranded for flexibility during installation, but are not sufficiently pliable to use as appliance cord. Cables for industrial, commercial and apartment buildings may contain many insulated conductors in an overall jacket, with helical tape steel or aluminium armour, or steel wire armour, and perhaps as well an overall PVC or lead jacket for protection from moisture and physical damage. Cables intended for very flexible service or in marine applications may be protected by woven bronze wires. Power or communications cables (e.g., computer networking) that are routed in or through air-handling spaces (plenums) of office buildings are required under

4961-447: Is stable when exposed to electricity, light, moisture, and extreme temperatures. It has superior electrical properties as an insulator and as a dielectric, and can support an electrostatic field while dissipating minimal energy in the form of heat; it can be split very thin (0.025 to 0.125 millimeters or thinner) while maintaining its electrical properties, has a high dielectric breakdown, is thermally stable to 500 °C (932 °F), and

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5082-463: Is the lowest that should be used (7 should only be used in applications where the wire is placed and then does not move), and 49 is much better. For applications with constant repeated movement, such as assembly robots and headphone wires, 70 to 100 is mandatory . For applications that need even more flexibility, even more strands are used (welding cables are the usual example, but also any application that needs to move wire in tight areas). One example

5203-451: Is therefore used as a window on radiation detectors such as Geiger–Müller tubes . In 2008, mica splittings represented the largest part of the sheet mica industry in the United States. Consumption of muscovite and phlogopite splittings was about 308 t in 2008. Muscovite splittings from India accounted for essentially all US consumption. The remainder was primarily imported from Madagascar. Small squared pieces of sheet mica are also used in

5324-414: Is unusual in that it is a good electrical insulator at the same time as being a good thermal conductor. The leading use of block mica is as an electrical insulator in electronic equipment. High-quality block mica is processed to line the gauge glasses of high-pressure steam boilers because of its flexibility, transparency, and resistance to heat and chemical attack. Only high-quality muscovite film mica, which

5445-723: Is used in decorative coatings on wallpaper, concrete, stucco , and tile surfaces. It also is used as an ingredient in flux coatings on welding rods, in some special greases, and as coatings for core and mold release compounds, facing agents, and mold washes in foundry applications. Dry-ground phlogopite mica is used in automotive brake linings and clutch plates to reduce noise and vibration ( asbestos substitute); as sound-absorbing insulation for coatings and polymer systems; in reinforcing additives for polymers to increase strength and stiffness and to improve stability to heat, chemicals, and ultraviolet (UV) radiation; in heat shields and temperature insulation; in industrial coating additive to decrease

5566-453: Is used in electric motor and generator armatures, field coil insulation, and magnet and commutator core insulation. Mica consumption in flexible plates was about 21 tonnes in 2008 in the US. A heater plate is used where high-temperature insulation is required. The molding plate is sheet mica from which V-rings are cut and stamped for use in insulating the copper segments from the steel shaft ends of

5687-455: Is used in industrial cables and power cables installed underground because of its superior moisture resistance. Insulated cables are rated by their allowable operating voltage and their maximum operating temperature at the conductor surface. A cable may carry multiple usage ratings for applications, for example, one rating for dry installations and another when exposed to moisture or oil. Generally, single conductor building wire in small sizes

5808-574: Is used in many types of electrical wiring. Aluminium wire was common in North American residential wiring from the late 1960s to mid-1970s due to the rising cost of copper. Because of its greater resistivity , aluminium wiring requires larger conductors than copper. For instance, instead of 14 AWG ( American wire gauge ) copper wire, aluminium wiring would need to be 12 AWG on a typical 15 ampere lighting circuit, though local building codes vary. Solid aluminium conductors were originally made in

5929-626: Is used primarily as an electrical insulation material. Mica insulation is used in high-temperature and fire-resistant power cables in aluminium plants, blast furnaces , critical wiring circuits (for example, defence systems, fire and security alarm systems, and surveillance systems), heaters and boilers, lumber kilns , metal smelters, and tanks and furnace wiring. Specific high-temperature mica-insulated wire and cable are rated to work for up to 15 minutes in molten aluminium, glass, and steel. Major products are bonding materials; flexible, heater, molding, and segment plates; mica paper; and tape. Flexible plate

6050-427: Is used to distribute power down the length of a building; it is constructed to allow tap-off switches or motor controllers to be installed at designated places along the bus. The big advantage of this scheme is the ability to remove or add a branch circuit without removing voltage from the whole duct. Bus ducts may have all phase conductors in the same enclosure (non-isolated bus), or may have each conductor separated by

6171-609: Is variously called India ruby mica or ruby muscovite mica, is used as a dielectric in capacitors . The highest quality mica film is used to manufacture capacitors for calibration standards . The next lower grade is used in transmitting capacitors . Receiving capacitors use a slightly lower grade of high-quality muscovite. Mica sheets are used to provide structure for heating wire (such as in Kanthal or Nichrome ) in heating elements and can withstand up to 900 °C (1,650 °F). Single-ended self-starting lamps are insulated with

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6292-417: The skin effect , resulting in increased power loss in the wire. Stranded wire might seem to reduce this effect, since the total surface area of the strands is greater than the surface area of the equivalent solid wire, but ordinary stranded wire does not reduce the skin effect because all the strands are short-circuited together and behave as a single conductor. A stranded wire will have higher resistance than

6413-489: The CO/ALR "copper-aluminium-revised" designation) were developed to reduce these problems. While larger sizes are still used to feed power to electrical panels and large devices, aluminium wiring for residential use has acquired a poor reputation and has fallen out of favour. Aluminium conductors are still heavily used for bulk power transmission , power distribution , and large feeder circuits with heavy current loads, due to

6534-453: The Nara period . Yatsuomote ware is a type of local Japanese pottery from there. After an incident at Mount Yatsuomote a small bell was offered to soothe the kami . Katō Kumazō started a local tradition where small ceramic zodiac bells (きらら鈴) were made out of local mica kneaded into the clay , and after burning in the kiln the bell would make a pleasing sound when rung. Ayurveda ,

6655-457: The Slinky toy, are made of special flattened wire. In antiquity , jewelry often contains large amounts of wire in the form of chains and applied decoration that is accurately made and which must have been produced by some efficient, if not technically advanced, means. In some cases, strips cut from metal sheet were made into wire by pulling them through perforations in stone beads. This causes

6776-612: The X ion is Ca, the mica is classed as a brittle mica. Brittle micas: Common micas: Brittle micas: Very fine-grained micas, which typically show more variation in ion and water content, are informally termed "clay micas". They include: Sericite is the name given to very fine, ragged grains and aggregates of white (colorless) micas. Mica is widely distributed and occurs in igneous , metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites . The largest documented single crystal of mica ( phlogopite )

6897-435: The monoclinic system, with a tendency towards pseudohexagonal crystals , and are similar in structure but vary in chemical composition. Micas are translucent to opaque with a distinct vitreous or pearly luster, and different mica minerals display colors ranging from white to green or red to black. Deposits of mica tend to have a flaky or platy appearance. The crystal structure of mica is described as TOT-c , meaning that it

7018-525: The 1930s, was knob and tube (K&T) wiring: single conductors were run through cavities between the structural members in walls and ceilings, with ceramic tubes forming protective channels through joists and ceramic knobs attached to the structural members to provide air between the wire and the lumber and to support the wires. Since air was free to circulate over the wires, smaller conductors could be used than required in cables. By arranging wires on opposite sides of building structural members, some protection

7139-455: The 1960s from a utility-grade aluminium alloy that had undesirable properties for a building wire, and were used with wiring devices intended for copper conductors. These practices were found to cause defective connections and fire hazards. In the early 1970s new aluminium wire made from one of several special alloys was introduced, and all devices – breakers, switches, receptacles, splice connectors , wire nuts , etc. — were specially designed for

7260-516: The Hindu system of ancient medicine prevalent in India, includes the purification and processing of mica in preparing Abhraka bhasma, which is claimed as a treatment for diseases of the respiratory and digestive tracts. Mica dust in the workplace is regarded as a hazardous substance for respiratory exposure above certain concentrations. The Occupational Safety and Health Administration (OSHA) has set

7381-491: The US is in the joint compound for filling and finishing seams and blemishes in gypsum wallboard ( drywall ). The mica acts as a filler and extender, provides a smooth consistency, improves the workability of the compound, and provides resistance to cracking. In 2008, joint compounds accounted for 54% of dry-ground mica consumption. In the paint industry, ground mica is used as a pigment extender that also facilitates suspension, reduces chalking, prevents shrinking and shearing of

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7502-445: The United States (53,000 t), South Korea (50,000 t), France (20,000 t) and Canada (15,000 t). The total global production was 350,000 t, although no reliable data were available for China. Most sheet mica was produced in India (3,500 t) and Russia (1,500 t). Flake mica comes from several sources: the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, and pegmatites. Sheet mica

7623-576: The Upper Paleolithic period (40,000 BC to 10,000 BC). The first hues were red ( iron oxide , hematite , or red ochre ) and black ( manganese dioxide , pyrolusite ), though black from juniper or pine carbons has also been discovered. White from kaolin or mica was used occasionally. A few kilometers northeast of Mexico City stands the ancient site of Teotihuacan . Mica was found in the noble palace complex "Viking Group" during an excavation led by Pedro Armillas between 1942 and 1944. Later,

7744-428: The added wire may be circular in cross-section ("round-wound"), or flattened before winding ("flat-wound"). Examples include: Mica Micas are used in products such as drywalls , paints , and fillers, especially in parts for automobiles, roofing, and in electronics. The mineral is used in cosmetics and food to add "shimmer" or "frost". The mica group comprises 37 phyllosilicate minerals . All crystallize in

7865-423: The benefit of air cooling. A variation is to use heavy cables, especially where it is desirable to transpose or "roll" phases. In industrial applications, conductor bars are often pre-assembled with insulators in grounded enclosures. This assembly, known as bus duct or busway, can be used for connections to large switchgear or for bringing the main power feed into a building. A form of bus duct known as "plug-in bus"

7986-419: The best surface properties of any filled plastic composite. In 2008, consumption of dry-ground mica in plastic applications accounted for 2% of the market. The rubber industry used ground mica as an inert filler and mold release compound in the manufacture of molded rubber products such as tires and roofing. The platy texture acts as an anti-blocking, anti-sticking agent. Rubber mold lubricant accounted for 1.5% of

8107-429: The bobbins; the latter being revolved at a suitable speed bodily with their disks, the cotton is consequently served on to the wire, winding in spiral fashion so as to overlap. If many strands are required the disks are duplicated, so that as many as sixty spools may be carried, the second set of strands being laid over the first. For heavier cables that are used for electric light and power as well as submarine cables,

8228-455: The conductors. Rubber insulation further inside the cable often is in better condition than the insulation exposed at connections, due to reduced exposure to oxygen. The sulfur in vulcanized rubber insulation attacked bare copper wire so the conductors were tinned to prevent this. The conductors reverted to being bare when rubber ceased to be used. About 1950, PVC insulation and jackets were introduced, especially for residential wiring. About

8349-685: The contact surface does not oxidise. Insulated wires may be run in one of several forms between electrical devices. This may be a specialised bendable pipe, called a conduit , or one of several varieties of metal (rigid steel or aluminium) or non-metallic ( PVC or HDPE ) tubing. Rectangular cross-section metal or PVC wire troughs (North America) or trunking (UK) may be used if many circuits are required. Wires run underground may be run in plastic tubing encased in concrete, but metal elbows may be used in severe pulls. Wiring in exposed areas, for example factory floors, may be run in cable trays or rectangular raceways having lids. Where wiring, or raceways that hold

8470-679: The current capacity (ampacity). Special sealed fittings are used for wiring routed through potentially explosive atmospheres. For very high currents in electrical apparatus, and for high currents distributed through a building, bus bars can be used. (The term "bus" is a contraction of the Latin omnibus – meaning "for all".) Each live ("hot") conductor of such a system is a rigid piece of copper or aluminium, usually in flat bars (but sometimes as tubing or other shapes). Open bus bars are never used in publicly accessible areas, although they are used in manufacturing plants and power company switch yards to gain

8591-562: The dress). Thin mica flakes are added to a hot starch water solution, and the dupatta is dipped in this water mixture for 3–5 minutes. Then it is hung to air dry. Throughout the ages, fine powders of mica have been used for various purposes, including decorations. Powdered mica glitter is used to decorate traditional water clay pots in India, Pakistan and Bangladesh; it is also used on traditional Pueblo pottery, though not restricted to use on water pots in this case. The gulal and abir (colored powders) used by North Indian Hindus during

8712-435: The dry-ground mica used in 2008. As a rubber additive, mica reduces gas permeation and improves resiliency. Dry-ground mica is used in the production of rolled roofing and asphalt shingles , where it serves as a surface coating to prevent sticking of adjacent surfaces. The coating is not absorbed by freshly manufactured roofing because mica's platy structure is unaffected by the acid in asphalt or by weather conditions. Mica

8833-458: The enclosures are separated. This type of bus can be rated up to 50,000 amperes and up to hundreds of kilovolts (during normal service, not just for faults), but is not used for building wiring in the conventional sense. Electrical panels are easily accessible junction boxes used to reroute and switch electrical services . The term is often used to refer to circuit breaker panels or fuseboxes. Local codes can specify physical clearance around

8954-649: The environmental conditions, such as ambient temperature range, moisture levels, and exposure to sunlight and chemicals. Associated circuit protection, control, and distribution devices within a building's wiring system are subject to voltage, current, and functional specifications. Wiring safety codes vary by locality, country, or region. The International Electrotechnical Commission (IEC) is attempting to harmonise wiring standards among member countries, but significant variations in design and installation requirements still exist. Materials for wiring interior electrical systems in buildings vary depending on: Wiring systems in

9075-491: The festive season of Holi contain fine crystals of mica to create a sparkling effect. The majestic Padmanabhapuram Palace , 65 km (40 mi) from Trivandrum in India, has colored mica windows. Mica powder is also used as a decoration in traditional Japanese woodblock printmaking , as when applied to wet ink with gelatin as thickener using kirazuri technique and allowed to dry, it sparkles and reflects light. Earlier examples are found among paper decorations, with

9196-689: The film at the mica-film interface is ultra-flat once the film is removed from the substrate. Freshly-cleaved mica surfaces have been used as clean imaging substrates in atomic force microscopy , enabling for example the imaging of bismuth films, plasma glycoproteins , membrane bilayers , and DNA molecules. Thin transparent sheets of mica were used for peepholes in boilers, lanterns, stoves , and kerosene heaters because they were less likely to shatter than glass when exposed to extreme temperature gradients. Such peepholes were also fitted in horse-drawn carriages and early 20th-century cars, where they were called isinglass curtains . The word mica

9317-499: The form of wire rope . In electricity and telecommunications signals , a "wire" can refer to an electrical cable , which can contain a "solid core" of a single wire or separate strands in stranded or braided forms. Usually cylindrical in geometry, wire can also be made in square, hexagonal, flattened rectangular, or other cross-sections, either for decorative purposes, or for technical purposes such as high-efficiency voice coils in loudspeakers . Edge-wound coil springs , such as

9438-533: The founders of the Company of Mineral and Battery Works , who had a monopoly on this. Apart from their second wire mill at nearby Whitebrook, there were no other wire mills before the second half of the 17th century. Despite the existence of mills, the drawing of wire down to fine sizes continued to be done manually. According to a description in the early 20th century, "[w]ire is usually drawn of cylindrical form; but it may be made of any desired section by varying

9559-437: The framing of the building or on running boards. Where conductors went through walls, they were protected with cloth tape. Splices were done similarly to telegraph connections, and soldered for security. Underground conductors were insulated with wrappings of cloth tape soaked in pitch, and laid in wooden troughs which were then buried. Such wiring systems were unsatisfactory because of the danger of electrocution and fire, plus

9680-483: The height as the Nishi Honganji 36 Poets Collection , codices of illuminated manuscripts in and after ACE 1112. For metallic glitter, Ukiyo-e prints employed very thick solution either with or without color pigments stencilled on hairpins, sword blades or fish scales on carp streamers ( 鯉のぼり , Koinobori ) . The soil around Nishio in central Japan is rich in mica deposits, which were already mined in

9801-539: The help of child labour . The commercially important micas are muscovite and phlogopite , which are used in a variety of applications. Mica's value is based on its unique physical properties: the crystalline structure of mica forms layers that can be split or delaminated into thin sheets usually causing foliation in rocks. These sheets are chemically inert, dielectric , elastic, flexible, hydrophilic, insulating, lightweight, platy, reflective, refractive, resilient, and range in opacity from transparent to opaque. Mica

9922-517: The high labour cost for such installations. The first electrical codes arose in the 1880s with the commercial introduction of electrical power; however, many conflicting standards existed for the selection of wire sizes and other design rules for electrical installations, and a need was seen to introduce uniformity on the grounds of safety. The earliest standardized method of wiring in buildings, in common use in North America from about 1880 to

10043-551: The hole and then drifting it out to correct diameter with a punch." Wire is often reduced to the desired diameter and properties by repeated drawing through progressively smaller dies, or traditionally holes in draw plates . After a number of passes the wire may be annealed to facilitate more drawing or, if it is a finished product, to maximise ductility and conductivity . Electrical wires are usually covered with insulating materials , such as plastic, rubber-like polymers, or varnish. Insulating and jacketing of wires and cables

10164-431: The hollow shaft. This disk has perforations through which each of the strands pass, thence being immediately wrapped on the cable, which slides through a bearing at this point. Toothed gears having certain definite ratios are used to cause the winding drum for the cable and the cage for the spools to rotate at suitable relative speeds which do not vary. The cages are multiplied for stranding with many tapes or strands, so that

10285-514: The individual conductors are wrapped in paper before the plastic jacket is applied. Special versions of non-metallic sheathed cables, such as US Type UF, are designed for direct underground burial (often with separate mechanical protection) or exterior use where exposure to ultraviolet radiation (UV) is a possibility. These cables differ in having a moisture-resistant construction, lacking paper or other absorbent fillers, and being formulated for UV resistance. Rubber-like synthetic polymer insulation

10406-406: The installation and wiring of electrical equipment in hazardous areas . Wires and cables are rated by the circuit voltage, temperature rating and environmental conditions (moisture, sunlight, oil, chemicals) in which they can be used. A wire or cable has a voltage (to neutral) rating and a maximum conductor surface temperature rating. The amount of current a cable or wire can safely carry depends on

10527-679: The installation conditions. The international standard wire sizes are given in the IEC 60228 standard of the International Electrotechnical Commission . In North America, the American Wire Gauge standard for wire sizes is used. Modern non-metallic sheathed cables, such as (US and Canadian) Types NMB and NMC, consist of two to four wires covered with thermoplastic insulation, plus a wire for Protective Earthing/Grounding (bonding), surrounded by

10648-471: The insulation, with an overall woven jacket, usually impregnated with tar as a protection from moisture. Waxed paper was used as a filler and separator. Over time, rubber-insulated cables become brittle because of exposure to atmospheric oxygen, so they must be handled with care and are usually replaced during renovations. When switches, socket outlets or light fixtures are replaced, the mere act of tightening connections may cause hardened insulation to flake off

10769-419: The interior of jacketed cables, where the cable passes through areas where flammable gases are present. To prevent loosening of the connections of individual conductors of a cable, cables must be supported near their entrance to devices and at regular intervals along their runs. In tall buildings, special designs are required to support the conductors of vertical runs of cable. Generally, only one cable per fitting

10890-611: The legal limit ( permissible exposure limit ) for mica exposure in the workplace as 20 million parts per cubic foot (706,720,000 parts per cubic meter) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 3 mg/m respiratory exposure over an 8-hour workday. At levels of 1,500 mg/m , mica is immediately dangerous to life and health . Some lightweight aggregates , such as diatomite , perlite , and vermiculite , may be substituted for ground mica when used as filler. Ground synthetic fluorophlogopite ,

11011-583: The loss of circulation by sealing porous sections of the drill hole. Well-drilling muds accounted for 15% of dry-ground mica use in 2008. The plastics industry used dry-ground mica as an extender and filler, especially in parts for automobiles as lightweight insulation to suppress sound and vibration. Mica is used in plastic automobiles fascia and fenders as a reinforcing material, providing improved mechanical properties and increased dimensional stability, stiffness, and strength. Mica-reinforced plastics also have high-heat dimensional stability, reduced warpage, and

11132-432: The lower-pitched sound-producing "strings" in stringed instruments , such as violins , cellos , and guitars , and percussive string instruments such as pianos , dulcimers , dobros , and cimbaloms . To increase the mass per unit length (and thus lower the pitch of the sound even further), the main wire may sometimes be helically wrapped with another, finer strand of wire. Such musical strings are said to be "overspun";

11253-416: The lowest number of strands usually seen is 7: one in the middle, with 6 surrounding it in close contact. The next level up is 19, which is another layer of 12 strands on top of the 7. After that the number varies, but 37 and 49 are common, then in the 70 to 100 range (the number is no longer exact). Larger numbers than that are typically found only in very large cables. For application where the wire moves, 19

11374-408: The machines are somewhat different in construction. The wire is still carried through a hollow shaft, but the bobbins or spools of covering material are set with their spindles at right angles to the axis of the wire, and they lie in a circular cage which rotates on rollers below. The various strands coming from the spools at various parts of the circumference of the cage all lead to a disk at the end of

11495-404: The model building code to be either encased in metal conduit, or rated for low flame and smoke production. For some industrial uses in steel mills and similar hot environments, no organic material gives satisfactory service. Cables insulated with compressed mica flakes are sometimes used. Another form of high-temperature cable is mineral-insulated cable , with individual conductors placed within

11616-520: The needle and fish-hook industries; nail, peg, and rivet making; and carding machinery consume large amounts of wire as feedstock. Not all metals and metallic alloys possess the physical properties necessary to make useful wire. The metals must in the first place be ductile and strong in tension, the quality on which the utility of wire principally depends. The principal metals suitable for wire, possessing almost equal ductility, are platinum , silver , iron , copper , aluminium, and gold ; and it

11737-532: The operation of a motor or generator. Consumption of segment plates was about 149 t in 2008 in the US. Some types of built-up mica have bonded splittings reinforced with cloth, glass, linen , muslin , plastic, silk, or special paper. These products are very flexible and are produced in wide, continuous sheets that are either shipped, rolled, or cut into ribbons or tapes, or trimmed to specified dimensions. Built-up mica products may also be corrugated or reinforced by multiple layering. In 2008, about 351 t of built-up mica

11858-401: The original hexahedral symmetry is discernible in the pseudohexagonal character of mica crystals. The short-range order of K ions on cleaved muscovite mica has been resolved. Chemically, micas can be given the general formula in which Structurally, micas can be classed as dioctahedral ( Y = 4) and trioctahedral ( Y = 6). If the X ion is K or Na, the mica is a common mica, whereas if

11979-538: The outline of the holes in the draw-plate through which it is passed in the process of manufacture. The draw-plate or die is a piece of hard cast-iron or hard steel, or for fine work it may be a diamond or a ruby . The object of utilising precious stones is to enable the dies to be used for a considerable period without losing their size, and so producing wire of incorrect diameter. Diamond dies must be re-bored when they have lost their original diameter of hole, but metal dies are brought down to size again by hammering up

12100-468: The paint film, increases the resistance of the paint film to water penetration and weathering and brightens the tone of colored pigments. Mica also promotes paint adhesion in aqueous and oleoresinous formulations. Consumption of dry-ground mica in paint, the second-ranked use, accounted for 22% of the dry-ground mica used in 2008. Ground mica is used in the well-drilling industry as an additive to drilling fluids . The coarsely ground mica flakes help prevent

12221-430: The panels. Squirrels , rats, and other rodents may gnaw on unprotected wiring, causing fire and shock hazards. This is especially true of PVC-insulated telephone and computer network cables. Several techniques have been developed to deter these pests, including insulation loaded with pepper dust. The first interior power wiring systems used conductors that were bare or covered with cloth, which were secured by staples to

12342-451: The permeability of moisture and hydrocarbons; and in polar polymer formulations to increase the strength of epoxies, nylons, and polyesters . Wet-ground mica, which retains the brilliance of its cleavage faces, is used primarily in pearlescent paints by the automotive industry. Many metallic-looking pigments are composed of a substrate of mica coated with another mineral, usually titanium dioxide (TiO 2 ). The resultant pigment produces

12463-591: The purpose. These newer aluminium wires and special designs address problems with junctions between dissimilar metals, oxidation on metal surfaces, and mechanical effects that occur as different metals expand at different rates with increases in temperature. Unlike copper, aluminium has a tendency to creep or cold-flow under pressure, so older plain steel screw clamped connections could become loose over time. Newer electrical devices designed for aluminium conductors have features intended to compensate for this effect. Unlike copper, aluminium forms an insulating oxide layer on

12584-579: The raw material of many important manufacturers , such as the wire netting industry, engineered springs, wire-cloth making and wire rope spinning, in which it occupies a place analogous to a textile fiber . Wire-cloth of all degrees of strength and fineness of mesh is used for sifting and screening machinery, for draining paper pulp, for window screens, and for many other purposes. Vast quantities of aluminium , copper , nickel and steel wire are employed for telephone and data cables , and as conductors in electric power transmission , and heating . It

12705-416: The rigidity of solid wire would produce too much stress as a result of movement during assembly or servicing; A.C. line cords for appliances; musical instrument cables; computer mouse cables; welding electrode cables; control cables connecting moving machine parts; mining machine cables; trailing machine cables; and numerous others. At high frequencies, current travels near the surface of the wire because of

12826-457: The same time, single conductors with a thinner PVC insulation and a thin nylon jacket (e.g. US Type THN, THHN, etc.) became common. Wire A wire is a flexible, round, bar of metal . Wires are commonly formed by drawing the metal through a hole in a die or draw plate . Wire gauges come in various standard sizes, as expressed in terms of a gauge number or cross-sectional area . Wires are used to bear mechanical loads , often in

12947-430: The smallest machines for cotton covering have a large drum, which grips the wire and moves it through toothed gears; the wire passes through the centre of disks mounted above a long bed, and the disks carry each a number of bobbins varying from six to twelve or more in different machines. A supply of covering material is wound on each bobbin, and the end is led on to the wire, which occupies a central position relatively to

13068-420: The strip wire drawing method. The strip twist wire manufacturing method was superseded by drawing in the ancient Old World sometime between about the 8th and 10th centuries AD. There is some evidence for the use of drawing further East prior to this period. Square and hexagonal wires were possibly made using a swaging technique. In this method a metal rod was struck between grooved metal blocks, or between

13189-494: The strips to fold round on themselves to form thin tubes. This strip drawing technique was in use in Egypt by the 2nd Dynasty ( c.  2890  – c.  2686  BCE ). From the middle of the 2nd millennium BCE most of the gold wires in jewelry are characterized by seam lines that follow a spiral path along the wire. Such twisted strips can be converted into solid round wires by rolling them between flat surfaces or

13310-442: The structure of a sheet of the mineral brucite , with magnesium or ferrous iron being the most common cation. A dioctahedral sheet has the structure and (typically) the composition of a gibbsite sheet, with aluminium being the cation. Apical oxygens take the place of some of the hydroxyl ions that would be present in a brucite or gibbsite sheet, bonding the tetrahedral sheets tightly to the octahedral sheet. Tetrahedral sheets have

13431-498: The surface. This is sometimes addressed by coating aluminium conductors with an antioxidant paste (containing zinc dust in a low-residue polybutene base) at joints, or by applying a mechanical termination designed to break through the oxide layer during installation. Some terminations on wiring devices designed only for copper wire would overheat under heavy current load and cause fires when used with aluminium conductors. Revised standards for wire materials and wiring devices (such as

13552-487: The system and a few buildings were wired with it, it was never adopted into the US National Electrical Code. Drawbacks of the system were that special fittings were required, and that any defect in the connection of the sheath would result in the sheath becoming energised. Armored cables with two rubber-insulated conductors in a flexible metal sheath were used as early as 1906, and were considered at

13673-503: The time a better method than open knob-and-tube wiring, although much more expensive. The first rubber-insulated cables for US building wiring were introduced in 1922 with US patent 1458803 , Burley, Harry & Rooney, Henry, "Insulated electric wire", issued 1923-06-12, assigned to Boston Insulated Wire and Cable   . These were two or more solid copper electrical wires with rubber insulation, plus woven cotton cloth over each conductor for protection of

13794-564: The time. Paper-insulated cables proved unsuitable for interior wiring installations because very careful workmanship was required on the lead sheaths to ensure moisture did not affect the insulation. A system later invented in the UK in 1908 employed vulcanised-rubber insulated wire enclosed in a strip metal sheath. The metal sheath was bonded to each metal wiring device to ensure earthing continuity. A system developed in Germany called "Kuhlo wire" used one, two, or three rubber-insulated wires in

13915-573: The traditional Japanese Kōdō ceremony to burn incense: A burning piece of coal is placed inside a cone made of white ash. The sheet of mica is placed on top, acting as a separator between the heat source and the incense, to spread the fragrance without burning it. Sheet mica is used principally in the electronic and electrical industries. Its usefulness in these applications is derived from its unique electrical and thermal properties and its mechanical properties, which allow it to be cut, punched, stamped, and machined to close tolerances. Specifically, mica

14036-656: The tray to maintain clearance between the conductors, but small control wiring is often installed without any intentional spacing between cables. Local electrical regulations may restrict or place special requirements on mixing of voltage levels within one cable tray. Good design practices may segregate, for example, low level measurement or signal cables from trays carrying high power branch circuits, to prevent induction of noise into sensitive circuits. Since wires run in conduits or underground cannot dissipate heat as easily as in open air, and since adjacent circuits contribute induced currents, wiring regulations give rules to establish

14157-510: The various advantages they offer over copper wiring. Aluminium conductors both cost and weigh less than copper conductors, so a much larger cross sectional area can be used for the same weight and price. This can compensate for the higher resistance and lower mechanical strength of aluminium, meaning the larger cross sectional area is needed to achieve comparable current capacity and other features. Aluminium conductors must be installed with compatible connectors and special care must be taken to ensure

14278-475: The wiring, must traverse fire-resistance rated walls and floors, the openings are required by local building codes to be firestopped . In cases where safety-critical wiring must be kept operational during an accidental fire, fireproofing must be applied to maintain circuit integrity in a manner to comply with a product's certification listing . The nature and thickness of any passive fire protection materials used in conjunction with wiring and raceways has

14399-766: Was afforded against short-circuits that can be caused by driving a nail into both conductors simultaneously. By the 1940s, the labor cost of installing two conductors rather than one cable resulted in a decline in new knob-and-tube installations. However, the US code still allows new K&T wiring installations in special situations (some rural and industrial applications). In the United Kingdom, an early form of insulated cable, introduced in 1896, consisted of two impregnated-paper-insulated conductors in an overall lead sheath. Joints were soldered, and special fittings were used for lamp holders and switches. These cables were similar to underground telegraph and telephone cables of

14520-679: Was consumed in the US, mostly for molding plates (19%) and segment plates (42%). Sheet mica is a versatile and durable material widely used in electrical and thermal insulation applications. It exhibits excellent electrical properties, heat resistance, and chemical stability. Technical grade sheet mica is used in electrical components, electronics, atomic force microscopy and as window sheets. Other uses include diaphragms for oxygen-breathing equipment, marker dials for navigation compasses, optical filters , pyrometers , thermal regulators, stove and kerosene heater windows, radiation aperture covers for microwave ovens, and micathermic heater elements. Mica

14641-526: Was found in Lacey Mine, Ontario , Canada ; it measured 10 m × 4.3 m × 4.3 m (33 ft × 14 ft × 14 ft) and weighed about 330 tonnes (320 long tons; 360 short tons). Similar-sized crystals were also found in Karelia , Russia . Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia (100,000 tonnes), Finland (68,000 t),

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