There are some materials in which the electrons move easily from one atom to another. It takes little energy to get the electrons moving in these materials. In other materials, the electrons will move, but not quite so easily. They get jumbled around and heat is created because of this. Then there are some materials which don’t allow electron movement at all. The degree to which the material resists the flow of electrons is called the resistance of the substance.

Any medium that allows electric current to flow through it is called a conductor. Metal is one such medium that allows electric current to flow from one place to another easily. Electric current flows through wire much like water flows through pipes. Metals have a low resistance to electron movement; most metals are good conductors. Copper is one of the best conductors, as are silver, gold, and aluminum. A common example of a conductor is the copper wire inside an electric cord.