Sometimes wires are stranded–multiple small cores bundled together. This results in greater potential for electricity flow (per amount of copper), and results in greater flexibility of the wire. Most of the cords you deal with on a daily basis are made from stranded copper cable.
But there are cases where solid core is important for other reasons. A solid core wire is stiffer and more difficult to bend, and will typically retain whatever shape it is bent into. But pump electricity through it for decades and it’ll last a lot longer and be more reliable than its stranded counterpart. This is why your house’s wiring typically uses solid core copper–doesn’t move once installed, and reliability is kinda important when it’s inside your walls.
Why are all the wires full of expensive metal if we only need the surface?
It depends!
Sometimes wires are stranded–multiple small cores bundled together. This results in greater potential for electricity flow (per amount of copper), and results in greater flexibility of the wire. Most of the cords you deal with on a daily basis are made from stranded copper cable.
But there are cases where solid core is important for other reasons. A solid core wire is stiffer and more difficult to bend, and will typically retain whatever shape it is bent into. But pump electricity through it for decades and it’ll last a lot longer and be more reliable than its stranded counterpart. This is why your house’s wiring typically uses solid core copper–doesn’t move once installed, and reliability is kinda important when it’s inside your walls.