Resistance wire is wire intended for making electrical resistors (which are used to control the amount of current in a circuit). It is better if the alloy used has a high resistivity, since a shorter wire can then be used. In many situations, the stability of the resistor is of primary importance, and thus the alloy's temperature coefficient of resistivity and corrosion resistance play a large part in material selection.
When resistance wire is used for heating elements (in electric heaters, toasters, and the like), high resistivity and oxidation resistance are important.
Sometimes resistance wire is insulated by ceramic powder and sheathed in a tube of another alloy. Such heating elements are used in electric ovens and water heaters, and in specialized forms for cooktops.__TOC__
Types Nichrome, a non-magnetic 80/20 alloy of nickel and chromium, is the most common resistance wire for heating purposes because it has a high resistivity and resistance to oxidation at high temperatures, up to . When used as a heating element, resistance wire is usually wound into coils.
Kanthal (Alloy 875/815), a family of iron-chromium-aluminium () alloys, is used in a wide range of high-temperature applications, up to about . One difficulty in using nichrome or kanthal wire is that common tin-based electrical solder will not bond with it, so the connections to the electrical power must be made using other methods such as crimp connectors or screw terminals.
Constantan () has a low temperature coefficient of resistivity, and as a copper alloy, it is easily soldered. Other constant-resistance alloys include manganin (), Cupron (),https://www.cartech.com/ssalloysprod.aspx?id=1940 Carpenter Technology, CBX Cupron® Alloy and Evanohm. It melts at about .
Balco () and similar alloys have very high, but more linear, temperature coefficients of resistivity, making them suitable for sensing elements.
Many elements and alloys have been used as resistance wire for special purposes. The table below lists the resistivity of some common materials. The resistivity of amorphous carbon actually has a range of .
MaterialResistivity (Ω-cmil/ft) () Aluminum 15.94 2.650 Brass 42.1 7.0 Carbon (amorphous) ≃23.8 ≃3.95 Constantan 272.97 45.38 Copper 10.09 1.678 Iron 57.81 9.61 Kanthal 842.19 140 Manganin 290 48.21 Molybdenum 32.12 5.34 Nichrome 675 112.2 Nichrome V 650 108.1 Nickel 41.69 6.93 Platinum 63.16 10.5 Stainless steel (304) 541 90 Steel (0.5% carbon) 100 16.62 Zinc 35.49 5.90
Trade names Trade names include: MWS Wire Ind.Carpenter Tech.Driver-HarrisHarrisonHoskinsJelliffKanthal MWS-875Alchrome 875HAI-FeCr AI 25Alloy 875Kanthal A-1 MWS-800EvanohmKarmaHAI-431Chromel RAlloy 800Nikrothal L MWS-675Tophet CNichromeHAI-NiCr 60Chromel CAlloy CNikrothal 6 MWS-650Tophet ANichrome VHAI-NiCr 80Chromel AAlloy ANikrothal 8 MWS-294CupronAdvanceHAI-CuNi 102CopelAlloy 45Cuprothal 294 MWS-180180 AlloyMidohmHAI-180Alloy 380Alloy 180Cuprothal 180 MWS-120BalcoHytemcoHAI-380Alloy 120 MWS-9090 Alloy#95 AlloyHAI-90Alloy 290Alloy 90Cuprothal 90 MWS-6060 AlloyLohmHAI-60Alloy 260Alloy 60Cuprothal 60 MWS-3030 Alloy#30 AlloyHAI-30Alloy 230Alloy 30Cuprothal 30
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