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Chapter One: Electrostatic

corresponds with the number of protons in the nucleus (positive charge), and so the
atom appears electrically neutral. Accordingly, in an object where positive and negative
electric elementary charges are in an equilibrium state, its surface shows no surplus on
charge.

In contrast to the localized protons, electrons in electrically conductive materials are
mobile and can transport charges. At this point, an explanation to the terms “positive
” and “negative” charges is added. Up to the eighteenth century, it was believed
that two different kinds of electricity exist.

1.1 Understanding Static Electricity:

The ancient Greeks observed that if you rub amber (fossilized tree
sap) on cloth the amber would acquire the ability to attract small bits of
straw and dried grass. It was later discovered that some other objects
would acquire similar properties when they are rubbed with fur and other
materials. This phenomenon is called static electricity. (The word “electricity”
is derived from the Greek word for amber.) The objects that acquire the
properties of static electricity are said to carry a net electric charge.
Objects that carry a net electric charge are said to be charged. The study
of static electricity is called electrostatics.

1.2 The Electric Charges

A plastic comb that you’ve run through your hair will pick up bits of
paper and other small objects. In both of these cases, two objects are
rubbed together. Why should rubbing an object cause forces and sparks?
What kind of forces are these? These are the questions with which we
begin our study of electricity.

Certainly, one fundamental property of electric charge is its
existence in the two varieties that were long ago named positive and
negative[2]. The electron’s charge is negative; its antiparticle, called a
positron, has a positive charge, but its mass is precisely the same as that
of the electron. The proton’s antiparticle is called simply an antiproton; its
electric charge is negative.

University of Babylon/ College of Science Department of Physics

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