 |
| Image attribution: Public domain by Stevebidmed via Pixabay |
Electricity doesn't just flow through any material. Some materials called conductors allow the passage of a current and others called insulators prevent it flowing. An example of a conductor is copper as used in electric cables and we cover these cables with PVC, an insulator which electricity cannot pass through easily. Conductors can be solids, gases or liquids, but typically they're metals. Some metals are better than others at conducting electricity, i.e. they have a higher conductivity or lower resistivity.
In order of increasing conductivity we have:
Platinum
Iron
Aluminium
Gold
Copper
Silver
Copper is widely used as a conductor in electronics, electrical appliances and for power cables. It's ductile (i.e. can be easily stretched and deformed into wires), malleable (can be easily depressed into shape by compressive forces) and relatively cheap.
Silver is more conductive than copper, but much more expensive.
Aluminium is less conductive than copper, but lighter and so is used for overhead distribution cables.
Gold is less conductive than copper and more expensive. However unlike copper, its desirable characteristic is that it doesn't tarnish, i.e. oxidise in air due to contact with oxygen. It doesn't react with other common compounds either. Electrical connectors are usually made of brass and often coated with nickel. However these can tarnish over time, and this results in a degradation in performance because the tarnish coating isn't very conductive. This is why more expensive audio/video connectors are coated with gold so that they don't tarnish, resulting in possible bad connections between equipment.