Engineering Comparison
Copper conducts electricity better per unit cross-section, while aluminum offers much lower density and often lower cost. Electrical design must compare ampacity, conductor size, weight, joints and installation requirements.
Conductivity
Copper has higher electrical conductivity than aluminum. To achieve similar resistance, an aluminum conductor typically requires a larger cross-sectional area.
Weight
Aluminum’s low density means that even with a larger conductor area, the final conductor can be much lighter. This is valuable in overhead transmission and large cable systems.
Connections
Joint design is critical. Aluminum forms an oxide layer and has different thermal expansion and creep behavior from copper. Approved connectors, surface preparation and installation torque are important for reliable terminations.
Cost and application
Copper is common in building wiring, motors, transformers, electronics and compact high-current components. Aluminum is widely used in overhead lines and larger power-distribution conductors where weight and economics are important.
Frequently asked questions
Why is aluminum wire larger than copper for the same current?
Because aluminum has lower electrical conductivity, so more cross-sectional area is needed to achieve similar resistance.
Is aluminum wiring unsafe?
Properly designed modern aluminum conductor systems can be safe. Problems arise when conductor type, connector compatibility, workmanship or maintenance are inadequate.
Which is better for motors?
Copper is common where compact windings and high conductivity are priorities, but design and economics can support aluminum in some applications.
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