Resistance wire is

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 ...

intended for making electrical

resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

s (which are used to control the amount of current in a circuit). It is better if the

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 ...

used has a high

resistivity 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 ...

, 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 A temperature coefficient describes the relative change of a physical property that is associated with a given change in temperature. For a property ''R'' that changes when the temperature changes by ''dT'', the temperature coefficient α is def ...

and corrosion resistance play a large part in material selection. When resistance wire is used for

heating element A heating element converts electrical energy into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element. Unlike the Peltier effect, this process is indepen ...

s (in

electric heater Electric heating is a process in which electrical energy is converted directly to heat energy at around 100% efficiency, using rather cheap devices. Common applications include space heating, cooking, water heating and industrial processes. ...

toaster A toaster is a small electric appliance that uses radiant heat to brown sliced bread into toast. Types Pop-up toaster In pop-up or automatic toasters, a single vertical piece of bread is dropped into a slot on the top of the toaste ...

s, and the like), high resistivity and

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 ...

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 upA double oven A ceramic oven An oven is a tool which is used to expose materials to a hot environment. Ovens contain a hollow chamber and provide a means of heating the chamber in a controlled way. In use since antiquity, they have been use ...

s and water heaters, and in specialized forms for

cooktop A cooktop (American English), stovetop (American English) or hob (British English), is a device commonly used for cooking that is commonly found in kitchens and used to apply heat to the base of pans or pots. Cooktops are often found integrated ...

s. __TOC__

Types

Nichrome Nichrome (also known as NiCr, nickel-chromium or chromium-nickel) is a family of alloys of nickel, chromium, and often iron (and possibly other elements) commonly used as resistance wire, heating elements in devices like toasters, electrical kett ...

, a non-

magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particl ...

80/20

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow t ...

and chromium, is the most common resistance wire for heating purposes because it has a high resistivity and resistance to oxidation at high temperatures. When used as a heating element, resistance wire is usually wound into coils. One difficulty in using nichrome 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. Kanthal (Alloy 875/815), a family of iron-chromium-aluminium (FeCrAl) alloys is used in a wide range of high-temperature applications.

Constantan Constantan is a proprietary name for a copper– nickel alloy also known as Eureka, Advance, and Ferry. It usually consists of 55% copper and 45% nickel. Its main feature is the low thermal variation of its resistivity, which is consta ...

u55Ni45has a low temperature coefficient of resistivity and as a copper alloy, is easily soldered. Other constant-resistance alloys include manganin u86Mn12Ni2 Cupron u53Ni44Mn3and Evanohm. The Evanohm family of nickel-chrome alloys i72Cr20Mn4Al3Si1 i73Cr20Cu2Al2Mn1Si have high resistance, low temperature coefficient of resistance, low electromotive force (

Galvani potential In electrochemistry, the Galvani potential (also called Galvani potential difference, or inner potential difference, Δφ, delta phi) is the electric potential difference between two points in the bulk of two phases. These phases can be two diffe ...

) when in contact with copper, high tensile strength, and also are very stable with regards to heat treatment.

Balco The Bay Area Laboratory Co-operative (BALCO) (1984–2003) was an American company led by founder and owner Victor Conte. In 2003, journalists Lance Williams and Mark Fainaru-Wada investigated the company's role in a drug sports scandal later re ...

i70Fe30and similar alloys have very high, but more linear, temperature coefficient 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 × 10⁻⁶ Ω m.

Trade names

Trade names include:

References

{{refs Wire Heating, ventilation, and air conditioning Resistive components