Lesson 1/Learning Event 1
SCOPE OF THIS LESSON
The complete study of electricity is a wide and complicated field. Even now, a lot of questions are
unanswered and there is still a lot to learn. This lesson is not designed to teach you all there is to
know about the subject. The information in this lesson will enable you to understand automotive
electricity so that you know what it is, what it is supposed to do, how it does it, and how to
determine what is wrong if there is trouble.
The word "electricity" comes from the Greek word "elektron" which means amber. More than
2,500 years ago, Thales, a famous Greek, found out that electricity existed. Thales noticed that
after he rubbed a piece of amber with a woolen cloth, the amber would attract lightweight items
like dust, straws, feathers, and lint. This was because the amber had become electrically charged.
Thales knew nothing about electricity, so he thought that this happened only with amber.
In 1733, a French scientist named Dufay found out that if a piece of glass was rubbed with cat's
fur, the glass and the cat fur would become charged or electrified. He also found out that the
charged glass would attract certain things that the fur would repel or push away. From this
experiment, he correctly decided there were two kinds of electricity that were directly opposite.
Benjamin Franklin decided the two kinds of electricity should be named POSITIVE and
NEGATIVE. They are also commonly referred to as plus and minus and are shown as (+) and (-).
"Positive," "plus," and "+" refer to one kind of electrical charge; "negative," "minus," and "-" refer
to the opposite charge.
Like charges repel each other, and unlike charges attract. Thus, if we have two items that have
positive charges, they will repel or push away from each other. The same action occurs if the items
have negative charges. On the other hand, if we have one item with a positive charge and another
item with a negative charge, they will attract or pull together.
For many years it was believed that only such things as glass, amber, silk, and cat's fur could be
electrified or charged. We know now, however, that under certain conditions all substances can be