History of Electricity:
The Greeks were the first to discover
electricity about 2500 years ago. They noticed
that when an amber was rubbed with other
materials it became charged with an unknown force that had the power to attract objects
such as dried leaves, feathers, bits of cloth, or other lightweight materials. The Greeks
called amber electron. The word electric was derived from it and meant
"to be like amber," or to have the ability to attract other objects.
This mysterious force remained little
more than a curious phenomenon until about 2000 years later, when other people began to
conduct experiments. In the early 1600s, William Gilbert discovered that amber was not the
only material that could be charged to attract other objects. He called materials that
could be charged electriks and materials that could not be charged noelectriks.
About 300 years ago a few men began to
study the behavior of various charged objects. In 1773, a Frenchman named Charles DuFay
found that a piece of charged glass would repel some charged objects and attract others.
These men soon learned that the force of repulsion was just as important as the
force of attraction. From these experiments, two lists were developed.
It was determined that any material in
list A would attract any material in list B, and that all materials in list A would repel
each other and all material in list B would repel each other. Various names were suggested
for the materials in lists A and B. Any opposite-sounding names could have been chosen,
such as east and west, north and south, male and female. Benjamin Franklin named the
materials in list A positive and the materials in list B negative . The
first item in each list was used as a standard for determining if a charged object was
positive or negative. Any object repelled by a piece of glass rubbed on silk would have a
positive charge and any item repelled by a hard rubber rod rubbed on wool would have a
negative charge.
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