View source for Resistance wire

{{Refimprove|date=September 2014}}

'''Resistance wire''' is [[wire]] intended for making electrical [[resistor]]s (which are used to control the amount of current in a [[electrical circuit|circuit]]).<ref>{{Cite web|url=http://www.pelicanwire.com/products/resistance-wire/|title = Resistance Wire}}</ref> It is better if the [[alloy]] used has a high [[Electrical resistivity and conductivity|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 [[Electrical resistivity and conductivity#Temperature dependence|temperature coefficient of resistivity]] and corrosion resistance play a large part in material selection.

When resistance wire is used for  [[heating element]]s (in [[electric heater]]s,  [[toaster]]s, and the like), high resistivity and [[oxidation]] resistance is important.

Sometimes resistance wire is insulated by ceramic powder and sheathed in a tube of another alloy. Such heating elements are used in electric [[oven]]s and [[water heating|water heaters]], and in specialized forms for [[cooktop]]s.

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==Types==
[[Nichrome]], a non-[[magnetism|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 {{convert|1400|C|F|lk=on}}. When used as a heating element, resistance wire is usually wound into coils.  

[[Kanthal (alloy)|Kanthal]] (Alloy 875/815), a family of iron-chromium-aluminium ({{chem2|FeCrAl}}) alloys, is used in a wide range of high-temperature applications, up to about {{convert|1425|°C|°F|abbr=on}}. 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 connection|crimp connectors]] or screw terminals.

[[Constantan]] ({{chem2|Cu55Ni45}}) has a low temperature coefficient of resistivity; and as a copper alloy, it is easily soldered. Other constant-resistance alloys include [[manganin]] ({{chem2|Cu86Mn12Ni2}}), Cupron  ({{chem2|Cu53Ni44Mn3}})<ref>https://www.cartech.com/ssalloysprod.aspx?id=1940 {{Webarchive|url=https://web.archive.org/web/20160720070204/http://www.cartech.com/ssalloysprod.aspx?id=1940 |date=2016-07-20 }} Carpenter Technology, CBX Cupron® Alloy</ref> and Evanohm. Melts at about {{convert|1220|°C|°F|abbr=on}}.

[[Balco alloy|Balco]] ({{chem2|Ni70Fe30}}) 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 3.8 – 4.1 × 10<sup>−6</sup> Ω m.

{| class="wikitable sortable"
! rowspan=2|Material
! colspan=2|Resistivity
|-
! (ohm-cmil/ft)
! (10<sup>−6</sup> ohm·cm)
|-
| 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 
|-
| 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:<ref>{{Cite web|url=http://www.pelicanwire.com/products/resistance-wire/|title = Resistance Wire}}</ref>

{| class="wikitable"
|-
! MWS Wire Ind.!!Carpenter Tech.!!Driver-Harris!!Harrison!!Hoskins!!Jelliff!!Kanthal
|-
| MWS-875||Alchrome 875||||HAI-FeCr AI 25||Alloy 875||||Kanthal A-1
|-
| MWS-800||Evanohm||Karma||HAI-431||Chromel R||Alloy 800||Nikrothal L
|-
| MWS-675||Tophet C||Nichrome||HAI-NiCr 60||Chromel C||Alloy C||Nikrothal 6
|-
| MWS-650||Tophet A||Nichrome V||HAI-NiCr 80||Chromel A||Alloy A||Nikrothal 8
|-
| MWS-294||Cupron||Advance||HAI-CuNi 102||Copel||Alloy 45||Cuprothal 294
|-
| MWS-180||180 Alloy||Midohm||HAI-180||Alloy 380||Alloy 180||Cuprothal 180
|-
| MWS-120||Balco||Hytemco||HAI-380||||Alloy 120||
|-
| MWS-90||90 Alloy||#95 Alloy||HAI-90||Alloy 290||Alloy 90||Cuprothal 90
|-
| MWS-60||60 Alloy||Lohm||HAI-60||Alloy 260||Alloy 60||Cuprothal 60
|-
| MWS-30||30 Alloy||#30 Alloy||HAI-30||Alloy 230||Alloy 30||Cuprothal 30
|}

== References ==

{{refs}}

[[Category:Wire]]
[[Category:Heating, ventilation, and air conditioning]]
[[Category:Resistive components]]