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Resistance wire is an alloy wire which produces some level of resistance to an electric current.

This resistance may be used for numerous reasons, including to control the amount of current in a circuit, and also as a heating element. The resistance of wire to conducting an electric current can generate heat, which is utilised in various products such as heaters, toasters, and hairdryers.

Other domestic applications of a resistance wire moreover include remote controls, light bulbs, and phone chargers.

The Resistance Of Wire Explained

Resistance of Wire

Resistance Wire Applications

However, resistance wire is not just used in domestic applications, despite these examples of everyday items. Resistance wire can be found across a range of industries and applications, including automotive and aerospace applications.

The quality of resistance wire is tightly controlled by BS 115 requirements (and BS 117 for wire diameters of less than 0.32mm) because of the many uses of resistance wire and its widespread applications.

Depending on the application, the combination of metals used within the resistance wire will change to increase or decrease resistance, or to suit the environment of its application – such as temperature. No matter of the alloy, resistance wire can be commonly found in varying lengths, from several metres to the great coils necessary for industrial use.

Still got questions regarding the resistance of wire? Let’s break it down further…

What Is Resistance Wire Used For?

Resistance wire uses include electrical resistors, which are used within an electrical circuit for various control measures.

Some examples include: temperature control; control of current (both fixed and variable); and to stop a circuit from shorting – this type of resistor is known as a fusible resistor.They can also be used for heating and lighting functions.

Resistance wires can be used for domestic, commercial, and industrial applications alike, relevant in industries spanning from oil and gas and industrial heating, to the medical sector.

Factors That Affect Resistance

There are four main factors which affect the resistance of wire; these should all be considered when calculating the overall resistance of wire. Resistance factors include:

Material – the natural resistivity of a material will affect the overall resistance. For instance, copper is more conductive than steel, so would have a low resistance to an electrical current.

Length – longer lengths of wire have increased resistance to an electrical current compared to shorter wires; this is known as a proportional relationship since resistance increases as length increases. This is because the electrons that carry the electric current through the wire collide with more ions the longer the wire is, making it more difficult for the current to flow.

Thickness – thickness or gauge, also known as the wire’s diameter or cross section, has an inversely proportional relationship to resistance. The thinner a wire is, the greater resistance it has; this is because thinner wire has fewer electrons to carry an electric current.

Temperature – heating a wire also increases the resistance of a wire. A hotter wire will have increased vibration, making it harder for electrons to carry the electric current without interruption from atoms.

Resistance v Resistivity

Though resistance and resistivity are closely related, they should not be used interchangeably since they refer to different measurements and resistance factors.

Resistance – marked by the symbol R – measures the overall resistance of wire. This includes resistivity, length, temperature, material, and gauge or thickness. Resistance is measured in Ohms.

Resistivity, on the other hand, refers to the natural resistance of a material or substance only. Resistivity is represented by the symbol ρ, and this measurement will not change as length or thickness changes. Resistivity is measured in Ohms-metres.

Though resistance and resistivity are separate measurements, they are proportionally related – the greater the natural resistivity of a material, the greater its overall resistance to an electric current.

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Resistance Wire Types

Resistance wire types refers to the combinations of metals within the wire which creates the alloy. The most common type of resistance wire is a nickel and chromium alloy which is used within heating applications. Other common types include constantan (a copper and nickel alloy) which is easily soldered, and a copper, manganese and nickel alloy.

Scott Precision Wire offers several resistance wire types, meeting all industrial needs. Our range of resistance wire includes:

Copper Magnesium: 0.2%; a high strength alloy
Copper and nickel alloys: created for low to medium temperature heating applications, with good corrosion resistance
Cromaloy 1: for good corrosion resistance and high temperature applications
Cromaloy 5: good resistance to oxide scaling and suitable for a range of applications from industrial furnaces to domestic toasters
Cromaloy A: great for high temperature applications with good resistance to Sulphur corrosion
Cumin 11: a copper-based alloy with manganese and nickel, which is suited for DC circuitry
Cupronic 2.5: a copper-based alloy with low resistivity, suitable for low temperature applications
Kutherm 3 & 10: a copper-based resistance wire, with elevated corrosion resistance and temperature resistance properties
Nickel 205: suitable for high temperature applications
Nickel Iron alloys: a self-limiting heating wire for increased temperature control
Stainless steel 304L: a low temperature resistance wire with high strength

For further information regarding Scott Precision Wire’s resistance wire types consult our technical data downloads, or speak to an expert member of our team directly.

Resistance Wire Calculator

As established when identifying resistance factors, the overall resistance of a wire can be calculated by identifying the resistivity, length, and thickness of a wire. A resistance wire calculator will use these factors to calculate overall resistance.
However, this can also be done manually. The equation used to calculate this is: resistance (R) = resistivity (ρ) multiplied by the division of wire length (L) over cross sectional area (A), or R = ρ (L / A).

Connecting Wires

Connecting wires can be used within a circuit; connecting wires resistance should not affect the circuit and they are assumed to have zero resistance, therefore connecting wires should have a low resistance. Copper is commonly used as a connecting wire since it is a highly conductive material.

Enamelled Wire Datasheets