What is the difference between copper and aluminum wires

In terms of conductivity, a copper wire is about twice as conductive as an aluminium wire of the same diameter. It will also be heavier though. If you compare two wires of the same weight and length (but different diameters, because of diffenrent density) they will be more or less equally conductive, maybe aluminum will even get the upper hand by weight.

In terms of mechanical properties, copper is much more elastic than aluminium in the sense that it is better at being bent/strecthed/pulled without being permanently deformed. Aluminium is very ductile, that is easily plied or formed, but it will not go back to its original shape or form. As a consequence aluminium is normally not used in stranded cables, as the stress on the individual strands when the cable is being flexed would cause some of them to break. Therefore aluminium cables are usually solid, which again means they become really stiff compared to a stranded copper cable of same amp rating.

Chemically, aluminium has extremely good resistance against corrosion, whereas copper is more vulnerable, although more resistant than steel. Galvanic corrosion due to current leaks to other conductive materials may however accelerate corrosion rapidly.

Last but not least aluminium is a lot cheaper than copper, and it is way cheaper to recycle.

In short, copper is more compact in volume, easier to pull but somewhat more expensive. Therefore copper cables are mostly used in smaller diameters serving all the end points of the power grid. For domestic houses and small scale buildings all cables will usually be of copper.

Aluminium cables are bulkier, harder to manhandle, but cheaper and very resistant. Consequently they are widely used for main power lines of high amperage serving a whole district or some major building facilities.

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