3.1 Copper Media
3.1.1 Atoms and Electrons
This lesson discusses the copper media used in networking. Since all matter is composed of
atoms, this page begins with a detailed explanation of atoms and electrons.
All matter is composed of atoms. The Periodic Table of Elements lists all known types of
atoms and their properties. The atom is comprised of three basic particles:
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Electrons – Particles with a negative charge that orbit the nucleus
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Protons – Particles with a positive charge
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Neutrons – Neutral particles with no charge
The protons and neutrons are combined together in a small group called a nucleus.
To better understand the electrical properties of different elements, locate helium (He) on the
periodic table.
Helium has an atomic number of 2, which means that helium has two protons and two
electrons. It has an atomic weight of 4. If the atomic number of 2 is subtracted from the atomic
weight of 4, the result shows that helium also has two neutrons.
The Danish physicist, Niels Bohr, developed a simplified model to illustrate the atom.
This illustration shows the model for a helium atom. If the protons and neutrons of an atom
were the size of adult soccer balls in the middle of a soccer field, the only thing smaller than
the balls would be the electrons. The electrons would be the size of cherries that would be in
orbit near the outer-most seats of the stadium. The overall volume of this atom would be
about the size of the stadium. The nucleus would be the size of the soccer balls.
Coulomb's Electric Force Law states that opposite charges react to each other with a force
that causes them to be attracted to each other. Like charges react to each other with a force
that causes them to repel each other. In the case of opposite and like charges, the force
increases as the charges move closer to each other. The force is inversely proportional to the
square of the separation distance. When particles get extremely close together, nuclear force
overrides the repulsive electrical force and keeps the nucleus together. That is why a nucleus
does not fly apart.
Examine the Bohr model of the helium atom. If Coulomb's law is true and the Bohr model
describes helium atoms as stable, then there must be other laws of nature at work. Review
both theories to see how they conflict with each other:
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Coulomb's law – Opposite charges attract and like charges repel.
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The Bohr model – Protons have positive charges and electrons have negative
charges. There is more than one proton in the nucleus.
Electrons stay in orbit, even though the protons attract the electrons. The electrons have just
enough velocity to keep orbiting and not be pulled into the nucleus, just like the moon around
the Earth.
Protons do not fly apart from each other because of a nuclear force that is associated with
neutrons. The nuclear force is an incredibly strong force that acts as a kind of glue to hold the
protons together.
Electrons are bound to their orbit around the nucleus by a weaker force than nuclear force.
Electrons in certain atoms, such as metals, can be pulled free from the atom and made to
flow. This sea of electrons, loosely bound to the atoms, is what makes electricity possible.
Electricity is a free flow of electrons.
Loosened electrons that do not move and have a negative charge are called static electricity.
If these static electrons have an opportunity to jump to a conductor, this can lead to
electrostatic discharge (ESD). Conductors will be discussed later in this module.
ESD is usually harmless to people. However, ESD can create serious problems for sensitive
electronic equipment. A static discharge can randomly damage computer chips, data, or both.
The logical circuitry of computer chips is extremely sensitive to ESD. Students should take
safety precautions before they work inside computers, routers, and similar devices.
Atoms, or groups of atoms called molecules, can be referred to as materials. Materials are
classified into three groups based on how easily free electrons flow through them.
The basis for all electronic devices is the knowledge of how insulators, conductors, and
semiconductors control the flow of electrons and work together.
The Lab Activity reviews the proper way to handle a multimeter.
The next page introduces voltage.