In domestic current-carrying wires, there are many thin copper wires inside the plastic insulation. Why is that so? Why can’t there be a single thick copper wire carrying the current instead of so many thin ones?
In: Engineering
There are several reasons. Multistrand wire is much more flexible as the different strands can slide against each other when bent while a solid wire is harder to bend but stay the shape you bent it into. There are advantages and disadvantages to both of these but in general solid wires are used for fixed intallations and multistrand wires are used for flexible installations like extension chords. Secondly if the wire is thick enough or the frequency is high enough then you start getting skin effects. Essentially the current will mostly travel over the skin of the wire and not reach the inside at all. By using a multistrand wire you are increasing the surface area of the wire and reducing the skin effect. This is partly why high voltage wires are multistranded wires. The third reason is that copper is a very good conductor of electricity but is not good at supporting its weight. So when you have long stretches of copper wire the copper might get damaged from being stretched out. One of the ways to fix this is to reinforce it by using some strands of steel alongside the copper strands when making the wire. The steel is lighter and stronger then the copper so the steel reinforcement will make the cable able to support more weight before getting damaged.
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