What makes a material an electrical conductor or insulator? Simply put, electrical conductors are materials that carry (or conduct) electrical currents well, such as iron and steel, and insulators are materials that do not, like glass and plastic.
Whether a substance conducts electricity is determined by how easily electrons move through it. Electrical conductivity depends on electron movement because protons and neutrons don't move—they are bound to other protons and neutrons in atomic nuclei. In addition to different types of materials, factors such as the size and temperature of materials also affect conductivity.
Conductors vs. Insulators
Valence electrons are like outer planets orbiting a star. They're attracted to their atoms enough to stay in position, but it doesn't always take a lot of energy to knock them out of place. Valence electrons easily carry electric currents. Inorganic substances like metals and plasmas that readily lose and gain electrons top the list of conductors.
On the other hand, organic molecules are typically insulators because their structure is primarily held together bystrong covalent bonds, and the presence of hydrogen bonding further contributes to their stability. This molecular structure doesn't easily allow electrons to move, which is necessary for electrical conductivity.
Some materials in pure form are insulators 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 create a superconductor. Pure water is an insulator, dirty water conducts weakly, and saltwater, with its free-floating ions, conducts well. However, most materials are neither good conductors nor good insulators but somewhere in the middle.
10 Electrical Conductors
The best electrical conductor, under conditions of ordinary temperature and pressure, is the metallic element silver. Silver is not always an ideal choice as a material, however, because it is expensive and susceptible to tarnishing, and the oxide layer known as tarnish is not conductive.
Similarly, rust, verdigris, and other oxide layers reduce conductivity even in the strongest conductors. The most effective electrical conductors are:
- Silver
- Gold
- Copper
- Aluminum
- Mercury
- Steel
- Iron
- Seawater
- Concrete
- Mercury
Other strong conductors include:
- Platinum
- Brass
- Bronze
- Graphite
- Dirty water
- Lemon juice
10 Electrical Insulators
Electric charges do not flow freely through insulators. This is an ideal quality in many cases—strong insulators are often used to coat or provide a barrier between conductors to keep electric currents under control. This can be seen in rubber-coated wires and cables. The most effective electrical insulators are:
- Rubber
- Glass
- Pure water
- Oil
- Air
- Diamond
- Dry wood
- Dry cotton
- Plastic
- Asphalt
Other strong insulators include:
- Fiberglass
- Dry paper
- Porcelain
- Ceramics
- Quartz
Other Factors That Influence Conductivity
The shape and size of a material affect its conductivity. For example, a thick piece of matter will conduct better than a thin piece of the same size and length. If you have two pieces of a material of the same thickness, but one is shorter than the other, the shorter one will conduct better because the shorter piece has less resistance, in much the same way that it's easier to force water through a short pipe than a long one.
Temperature also affects conductivity. As temperature increases, atoms and their electrons gain energy. Some insulators like glass are poor conductors when cool but good conductors when hot; most metals are better conductors when cool and less efficient conductors when hot. Some good conductors become superconductors at extremely low temperatures.
Sometimes conduction itself changes the temperature of a material. Electrons flow through conductors without damaging the atoms or causing wear. Moving electrons do experience resistance, though. Because of this, the flow of electrical currents can heat conductive materials.
Key Takeaways
- Metals and plasmas readily conduct electricity because their valence electrons can move easily.
- Insulators, often organic molecules, are primarily held together by strong covalent bonds, impeding electron movement and hindering electrical conductivity.
- Material factors like doping or impurities can also affect conductivity; for example, pure water is an insulator, but saltwater conducts due to free-floating ions.
