Electric Power Equipment - Introduction

Conductors, Semiconductors, and Insulators

Electric current is able to flow through almost all substances. However, the ease with which electricity can flow depends upon the nature of the substance. Substances that offer little resistance to the flow of electricity are known as good conductors. Examples: copper and steel. On the other hand, substances which impede the flow of electricity are known as bad conductors. Examples: Dry wood and rubber.

Going into more detail we place all substances into one of three categories:

a. CONDUCTORS

b. SEMICONDUCTORS

c. INSULATORS

This classification is dependent on their ability to conduct electric current.

Conductors are those elements which readily conduct electricity. Insulators have an extremely high resistance to the flow of electricity. All other matter between these two extremes is referred to as semiconductors.

The electrical conductivity of matter is dependent upon the atomic structure of the material from which the conductor is made. In any solid material, such as copper, as in all solids the atoms which make up the molecular structure are bound together firmly. However, some of the electrons are not bound to specific atoms – these electrons move from one atom to another. The electrons that are able to move around are referred to as the “free electrons.” Good conductors contain a lot of free electrons and the insulators do not have many free electrons.

Under normal circumstances, the free electrons move around in a haphazard manner. Therefore at any time no region of the substance is electron-rich or electron-poor. Sometimes we subject these electrons to an external force, which causes most of them to move in one direction. This movement of electrons, as a group, in one direction is referred to as ELECTRIC CURRENT.

Some metals are better conductors of electricity than others. Silver, copper, gold, and aluminum are materials with many free electrons and make good conductors. Silver is the best conductor, followed by copper, gold, and aluminum. Copper is used more often than silver because of lower cost. Aluminum is used where weight is a major consideration.