How do you tell whether a material is a conductor or an insulator? A material that transmits energy is a conductor, while one that resists energy transfer is an insulator. There are different types of conductors and insulators because there are different forms of energy. Materials that conduct electrons, protons, or ions are electrical conductors. They conduct electricity. Materials that conduct heat are thermal conductors. Substances that transfer sound are acoustical conductors. There are corresponding insulators for each type of conductor.
Many materials are both electrical and thermal conductors or insulators. However, there are exceptions, so don’t assume just because a sample conducts (insulates) one form of energy that it behaves the same for other forms! Here are examples of electrical and thermal conductors and insulators.
Electric Conductor Examples
Usually, electrical conductors have loosely bound electrons. Most metals are excellent electric conductors. The element that is the best electrical conductor is silver. Liquids that contain ions also conduct electricity. These include salt solutions, acids, and bases.
Electric Insulator Examples
Most organic materials are electric insulators because electrons aren’t as free to move in covalent bonds. Sea water contains ions and conducts electricity, but pure water is an electric insulator. Some elements can be conductors or insulators, depending on their form or allotrope. Graphite is an electric conductor, while diamond is an electric insulator.
- Dry wood
- Dry paper
- Pure water
- Beryllium oxide
Thermal Conductor Examples
Most metals conduct heat as well as electricity. But, electrical and thermal conductivity don’t always go hand-in-hand. For example, diamond is an electric insulator, but an excellent thermal conductor. Crystalline materials often conduct heat.
- Stainless steel
- Beryllium oxide
- Carbon nanotubes
Thermal Insulator Examples
Thermal insulators resist the flow of heat. Building and clothing materials are often insulators. Although you might expect glass to be a thermal conductor, it’s actually an insulator. Thermal insulators either contain open space in their structure or else their atoms and molecules are irregularly arranged.
- Polystyrene foam
- Mineral wool
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- Bird, R. Byron; Stewart, Warren E.; Lightfoot, Edwin N. (2007). Transport Phenomena (2nd ed.). John Wiley & Sons, Inc.. ISBN: 978-0-470-11539-8
- S. L. Kakani, S. L. (2005). Electronics Theory and Applications. New Age International. ISBN: 978-81-224-1536-0.