Resistance wire
Encyclopedia
Resistance wire is electrical wire
used for its property of electrical resistance. It is routinely used at high temperatures, so normally also has high melting point.
Resistance wire is usually used for high-power resistor
s and heating element
s, which produce heat used in electric heaters, electric oven
s and toaster
s, and many other appliances.
, a non-magnetic
alloy
of nickel
and chromium, is commonly used to make resistance wire 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.
Constantan
is used where resistance is required to not change with temperature. Constantan is readily solderable, though soldered joints have limited temperature range.
Many elements and alloys have been used as resistance wire for special purposes. The table below lists the resistivity of some common materials, with copper included as a comparison.
Wire
A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various...
used for its property of electrical resistance. It is routinely used at high temperatures, so normally also has high melting point.
Resistance wire is usually used for high-power resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s and heating element
Heating element
A heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element....
s, which produce heat used in electric heaters, electric oven
Oven
An oven is a thermally insulated chamber used for the heating, baking or drying of a substance. It is most commonly used for cooking. Kilns, and furnaces are special-purpose ovens...
s and toaster
Toaster
The toaster is typically a small electric kitchen appliance designed to toast multiple types of bread products. A typical modern two-slice toaster draws anywhere between 600 and 1200 W and makes toast in 1 to 3 minutes...
s, and many other appliances.
Types
NichromeNichrome
Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various...
, a non-magnetic
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
of nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
and chromium, is commonly used to make resistance wire because it has a high resistivity
Resistivity
Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. The SI unit of electrical resistivity is the ohm metre...
and resistance to oxidation at high temperatures. When used as a heating element, resistance wire is usually wound into coils.
Constantan
Constantan
Constantan is a copper-nickel alloy usually consisting of 55% copper and 45% nickel.Also known as Eureka.Its main feature is its resistivity which is constant over a wide range of temperatures...
is used where resistance is required to not change with temperature. Constantan is readily solderable, though soldered joints have limited temperature range.
Many elements and alloys have been used as resistance wire for special purposes. The table below lists the resistivity of some common materials, with copper included as a comparison.
| Material | Resistance (ohm-cmil/ft) |
Resistance (ohm-cm) |
|---|---|---|
| Aluminum | 15.94 | 2.650 e-6 |
| Brass | 42.1 | 7.0 e-6 |
| Carbon (amorphous) | 3.8-4.1 e-6 | |
| Constantan | 272.97 | 45.38 e-6 |
| Copper | 10.09 | 1.678 e-6 |
| Iron | 57.81 | 9.61 e-6 |
| Manganin | 290 | 48.21 e-6 |
| Molybdenum | 32.12 | 5.34 e-6 |
| Nichrome | 675 | 112.2 e-6 |
| Nichrome V | 650 | 108.1 e-6 |
| Nickel | 41.69 | 6.93 e-6 |
| Platinum | 63.16 | 10.5 e-6 |
| Stainless steel (304) | 541 | 90 e-6 |
| Steel (0.5% carbon) | 100 | 16.62 e-6 |
| Zinc | 35.49 | 5.90 e-6 |