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Chapter One: Electrostatic

CHAPTER 1

ELECTROSTATICS, Electricity, CHARGES AND
FIELDS

1. Introduction:

The early Greeks discovered that a piece of amber that has been
rubbed briskly can attract feathers or small pieces of straw. They also
found that certain stones from the region they called Magnesia can pick up
pieces of iron. These first experiences with the forces of electricity and
magnetism began a chain of investigations that has led to today's high-
speed computers, lasers, fiber-optic communications, and magnetic
resonance imaging, as well as modern miracles such as the light bulb.
Greeks did were exploring the concept of electric charge by looking at the
forces between objects that have been briskly rubbed. It is easy to make
systematic observations of how charges behave, and we will be led to
consider the forces between charges and how charges behave in different
materials. Electric current, whether it be for lighting a lightbulb or
changing the state of a computer memory element, is simply a controlled
motion of charges through conducting materials. One of our goals will be to
understand how charges move through electric circuits.

Principles of Static Electricity

Static electricity deals with phenomena due to attractions or repulsions of electric
charges. The presence of electrical charge manifests itself in forces between charged
bodies (see Figure 1)[1]. Coulomb was the first to express the empirical relation
between charge, force, and distance for electrical fields. The magnitude of force
between two electrical charges depends on the magnitude of charges themselves; the
force is inversely proportional to the square of the distance between them. This is
important to comprehend the mechanism of charging by contact and separation (see
Figures 2–4).

University of Babylon/ College of Science Department of Physics

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