Chapter 8 Electrical Engineering 137
how it is created, how it is transmitted and
controlled, how it is changed into a form of
energy that meets human needs and wants, and,
most importantly, how to deal with electricity in
a safe manner.
Electricity on the Atomic Level
To understand electricity, or the movement
of electrons, it is important to fi rst understand
the atom. All matter is made up of microscopic
building blocks called atoms, which are like
microscopic models of our solar system. The
planets in our solar system orbit around the sun.
In much the same way, atoms are made up of
electrons, protons, and neutrons. Negatively
charged subatomic particles called electrons
orbit around a nucleus, which is made up of
positively charged protons and electrically
neutral neutrons. Figure 8-3 shows a diagram of
an atom.
Most atoms have an equal number of protons
and electrons, which makes them electrically
neutral. Under normal circumstances these atoms
are stable. When an outside force like energy is
introduced to an atom, it becomes excited. If
the atom becomes excited enough, it can lose
electrons from its outer ring, which is called the
valence shell. Ions are electrically charged atoms.
Atoms that gain an electron take on a negative
charge and become negative ions. Atoms that lose
an electron take on a positive charge and become
positive ions. The fewer the electrons in the
valence shell, the more easily an atom can share
electrons. The concept of electrons moving from
one atom to another is critical to understanding
electricity.
Stephen Coburn/Shutterstock.comktttSh/bC St h
Figure 8-2.
Several electrical
engineers are a part of
the Institute of Electrical
and Electronics
Engineers.
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Nucleus
This single valence
electron can easily
be shared
Copper (Cu 29)
This atom shows protons, neutrons, and electrons.
Figure 8-3.
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