Wire Conductor Materials

Properties of common conductor materials. Resistivity determines how much a wire resists current flow; density affects weight; the temperature coefficient shows how resistance changes with heat.

Conductor Materials

Copper (Cu)

The standard conductor for electrical wiring. Excellent conductivity, ductility, and corrosion resistance.

Resistivity: 1.72 × 10⁻⁸ Ω·m

Density: 8,960 kg/m³

Temp coeff: 0.00393/°C

Aluminum (Al)

Lighter and cheaper than copper but requires larger gauge for equivalent ampacity. Common in utility and feeder applications.

Resistivity: 2.65 × 10⁻⁸ Ω·m (pure); 2.83 × 10⁻⁸ for EC-1350 wire (61% IACS)

Density: 2,700 kg/m³

Temp coeff: 0.00429/°C (pure); 0.00403/°C for EC-1350

Silver (Ag)

Highest electrical conductivity of any metal. Used in specialized high-performance applications.

Resistivity: 1.59 × 10⁻⁸ Ω·m

Density: 10,490 kg/m³

Temp coeff: 0.0038/°C

Gold (Au)

Excellent corrosion resistance and reliable contact properties. Used for connectors and thin plating.

Resistivity: 2.44 × 10⁻⁸ Ω·m

Density: 19,300 kg/m³

Temp coeff: 0.0034/°C

Nickel (Ni)

High-temperature resistance and corrosion resistance. Used in thermocouples and heating elements.

Resistivity: 6.99 × 10⁻⁸ Ω·m

Density: 8,900 kg/m³

Temp coeff: 0.006/°C

Nichrome (NiCr)

Nickel-chromium alloy with very high resistance. The standard material for heating elements.

Resistivity: 1.10 × 10⁻⁶ Ω·m

Density: 8,400 kg/m³

Temp coeff: 0.0004/°C

Steel (Fe)

High tensile strength but poor conductivity. Used where mechanical strength matters more than electrical performance.

Resistivity: 1.43 × 10⁻⁷ Ω·m

Density: 7,850 kg/m³

Temp coeff: 0.005/°C

Tinned Copper (Sn-Cu)

Copper wire coated with tin for improved corrosion resistance. Standard for marine and harsh environments.

Resistivity: 1.78 × 10⁻⁸ Ω·m

Density: 8,900 kg/m³

Temp coeff: 0.00393/°C

Frequently Asked Questions

What is the most conductive wire material?

Silver is the most conductive metal (resistivity 1.59 × 10⁻⁸ Ω·m), followed by copper (1.72), gold (2.44), and aluminum (2.65). In practice, copper is the standard for electrical wiring because it balances high conductivity with affordable cost. Silver is reserved for specialized connectors and RF applications.

Why is copper used for electrical wiring?

Copper is used because it combines high conductivity (second only to silver), good ductility, resistance to corrosion, and relatively affordable cost. It is also easy to solder and crimp, compatible with most connectors, and has decades of proven performance in both residential and industrial wiring.

When is aluminum wire used instead of copper?

Aluminum is used for large conductors (10 AWG and above) where weight and cost matter: service entrance cables, utility transmission lines, and large feeder runs to sub-panels. Aluminum wire is about 1/3 the cost and 1/3 the weight of copper, but requires 1.6× larger cross-section for the same conductivity.

What is nichrome wire used for?

Nichrome (nickel-chromium alloy) is used as a heating element in toasters, hair dryers, electric heaters, and kilns because of its high resistivity and resistance to oxidation at high temperatures. It generates heat efficiently when current passes through it and can withstand temperatures over 1000°C without burning out.

Wire types and insulation ratings → NEC Table 310.16 — conductor ampacity →