why are many over heated power cables made out of alluminum with a steel core?

Question

if possible use the following data to help you.

material aluminum

resistance/ohm 3

force needed to break wire/n 150

density/kg per m3 2700

cost of wire/$ 4

material copper

resistance/ohm 2

force needed to break wire/n 300

density/kg per m3 8900

cost of wire/$ 14

material steel

resistance/ohm 30

force needed to break wire/n 1500

density/kg per m3 7700

cost of wire/$ 1

Answer 1

Loads of data here...
First, I guess you mean "overhead" cable.
The reasons are simple:
1. The OUTER shell of the cable is made of several strands of ALUMINIUM. Reasons: 1. Although not the lowest electrical resistance (copper is better), it is much cheaper than copper (ratio 14/4 cheaper). 2. The good conductivity of the outershell allows the "pellicular effect" of the current to flow in an easy manner. The problem of aluminium is that it cannot support its own weight over long distances and will break.
2. The CENTER core is made of STEEL. Reasons: it is cheap and offer high traction resistance.
So, Alu for current and Steel for mechanical resistance.