Electricity Explained

Getting Down To Basics

By Bruce W. Maki

Conductors and Insulators

Conductors

If a material allows free electrons to move easily from one atom to another then we call that material a conductor. As we said earlier, most metals let their free electrons roam, so most metals are good conductors.

Silver is the best conductor. Copper is almost as good at conducting as silver, and it costs a lot less, so copper is the most popular material used in electrical pathways, or circuits.

Wires are the most familiar component of electrical circuits. Many of the materials that are good electrical conductors are also good conductors of heat.

Insulators

The atoms of some materials have no free electrons in their outer orbits. These electrons are busy doing other jobs, like being shared in the orbits of two adjacent atoms. They are so closely held that it is very difficult to pull them away. Most compounds of carbon and hydrogen are like this.

The hydrogen atom has only one electron, but it naturally wants two electrons for its outer (and only) orbital shell. Carbon has four electrons spinning in its outer shell, a shell that is most stable (or most satisfied) with eight electrons. So when hydrogen and carbon atoms are put close together, they stick together.

Carbon will easily connect with four hydrogen atoms, or many combinations of other carbon atoms and hydrogen atoms. The adjacent atoms share their outermost electrons and then each atom has satisfied and stable electron orbits, which means no free electrons.

Plastics, whose molecules are made from long combinations of carbon and hydrogen atoms, have few or no free electrons. This means that plastics are poor conductors of electricity (and they are also poor conductors of heat).

Being a poor conductor is good. We call these materials insulators. Insulating materials are very useful, they help us keep electricity where we want it. Today, most indoor electrical insulators are made from plastic, because it is durable and economical. Outdoors, such as on the utility poles serving your home, glass or ceramics are often used for insulators.