The diagram shows the cross-section of an overhead power cable. Strands of one metal surround a central core of a different metal. Why is aluminium used for...
Question 1 Report
The diagram shows the cross-section of an overhead power cable. Strands of one metal surround a central core of a different metal.
Why is aluminium used for the outer strands rather than copper?
Answer Details
The outer strands are aluminium because aluminium has a lower density, making the cable lighter. At about 2.7 g/cm3 it is roughly one third as dense as copper at 8.9 g/cm3, so a long span between pylons weighs far less and sags much less. Its oxide layer also stops it corroding in the open air.
Copper is in fact the better conductor, so conductivity is not the reason; aluminium conducts well enough and the weight saving decides the matter. Aluminium is not magnetic, and saying it does not conduct contradicts its use as the current-carrying strands in the diagram.
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