Conductors and insulators
For electrical energy to be used, an electrical circuit is necessary. You may have already made simple electric circuits and observed that some things will allow electric current to flow through (conductors) them while others prevent any movement of charge (insulators).
You can explore conductors and insulators with an interactive simulation in the interactive learning guide. Download the Circuit Construction (Part 1) activity.
Materials which allow charge to flow through a circuit easily. The most common conductors are made from metallic elements. Copper is the most common metal used to make wires. Silver and gold are very good conductors. However, the high cost of these metals limit their use in particular applications. There are also non-metal conductors like graphite (a form of pure carbon) or solutions of salts (forming electrically charged ions) that will conduct electricity but they have more resistance.
Materials which usually prevent charges from flowing through a circuit. They can be forced to conduct electricity if the charges have enough energy, i.e. if the voltage is high enough. This is evident during a lightning storm when the air, normally a very good insulator, is turned into a conductor to allow the lightning bolt to travel through the air.
The main difference between a conductor and insulator is how strongly the electrons are held in the chemical bonds between the atoms, and how easily they can be mobilised to move as an electric current. The elements we refer to as metals have an atomic arrangement that allow their outermost valence electrons to move very easily between atoms. The purer the metal the more easily the electrons are able to move.
In non-metal elements the electrons are held much more tightly in the chemical bonds that hold the atoms together. This means they will resist the motion of charge through them, i.e they have a very high electrical resistance. We normally call the materials with very high resistances an insulator. In the best insulators, like plastic, the electrons are held very tightly into atomic bonds and if electricity is to pass through them it requires a very high voltage. This results in the material being degraded, e.g. burnt.
Since all conductors, except superconductors, have some resistance and all insulators will conduct some current if they are forced to, this means there is no absolute dividing line between conductors and insulators. The terms are convenient when we are dealing with the usual voltages encountered in a laboratory.
Note: All insulators can be made to conduct if the potential difference (voltage) is large enough.
Could your body be a conductor of electricity?
Humans are not generally considered a conductor but we all know that people can die from an electric shock.
If the voltage of the source is high enough, there is a good chance that the charges will have enough energy to turn your body into a conductor.
An electric shock occurs when an electricity source causes a sufficient current to enter and exit the human body through the skin, muscles or hair. Burns are the most common injury from electric shock.