How Electrical Conductors and Insulators Work
Electrical conductors are materials that conduct electricity; insulators don’t. Why? Whether a substance conducts electricity depends on how easily electrons can move through it. Protons don’t move because, while they would carry electrical charge, they are bound to other protons and neutrons in atomic nuclei. Valence electrons are like outer planets orbiting a star. They are attracted enough to stay in position, but it doesn’t always take a lot of energy to knock them out of place. Metals readily lose and gain electrons, so they rule the list of conductors. Organic molecules are mostly insulators, in part because they are held together by covalent (shared electron) bonds and also because hydrogen bonding helps stabilize many molecules. Most materials are neither good conductors, nor good insulators. They don’t readily conduct, but if enough energy is supplied, the electrons will move.
Some materials are insulators in pure form, but will conduct if they are doped with small quantities of another element or if they contain impurities. For example, most ceramics are excellent insulators, but if you dope them, you can get a superconductor. Pure water is an insulator, but dirty water conducts weakly and salt water, with its free-floating ions, conducts well.
10 Electrical Conductors
The best electrical conductor, under conditions of ordinary temperature and pressure, is the metallic element silver. It’s not always an ideal choice as a material, though, because of its cost and because it tarnishes. The oxide layer known as tarnish is not conductive. Similarly, rust, verdigris, and other oxide layers reduce conductivity.
- sea water
- dirty water
- lemon juice
10 Electrical Insulators
- pure water
- dry wood
- dry cotton
- dry paper
It’s worth noting the shape and size of a material affects conductivity. A thick piece of matter will conduct better than a thin piece of the same length. If you take two pieces of a material that are the same thickness, but one is shorter than the other, the shorter one will conduct better. It has less resistance, in much the same way it’s easier to force water through a short pipe than a long one.
Temperature also affects conductivity. As increase temperature, atoms and their electrons gain energy. Some insulators (e.g., glass) are poor conductors when cool, yet good conductors when hot. Most metals are better conductors when cool and poorer conductors when hot. Some good conductors become superconductors at extremely low temperatures.
Although electrons flow through a conductive material, they don’t damage the atoms or cause wear, like you would get from friction of water in a canyon, for example. Moving electrons do experience resistance or cause friction, however. The flow of electrical current can lead to heating of a conductive material.