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Welcome to Module 2, Fundamentals of Electricity. This module will cover the
fundamentals of electricity in a practical way, and will not be complicated by
complex theory and mathematical calculations. The module will present a number of
different topics. You will be introduced to information that will be used in later
modules.
Like the other modules in this series, this one presents small, manageable sections
of new material followed by a series of questions about that material. Study the
material carefully, then answer the questions without referring back to what you’ve
just read. You are the best judge of how well you grasp the material. Review the
material as often as you think necessary. The most important thing is establishing a
solid foundation on which to build as you move from topic to topic and module to
module.
Key points are in bold.
Glossary items are italicized and underlined the first time they appear.
You may view definitions of glossary items by clicking on terms and words that are
underlined and italicized in the text. You may also browse the Glossary by clicking
on the Glossary bookmark in the left-hand margin.
We will start with an overview to introduce you to the main points about these
devices, and the parts that make them. Then we will step through each of these
topics in detail:
Section Title Page Number
· Introduction to Electricity 3
· Characteristics 3
· Current 4
· Voltage 5
· Resistance 6
· Review 1 9
· Ohm’s Law 10
· DC Circuits 10
· Series Circuits 11
· Parallel Circuits 13
· Review 2 17
· AC Voltage 19
· Magnetism & Electromagnetism 19
· Alternating Current (AC) 22
· Sine Waves 22
· AC vs. DC 25
· AC Voltage — Single-Phase and Three-Phase 25
· Sine Wave Values 26
· Review 3 28
· Electric Power 30
· Calculating Power 30
· Kilowatt 31
· Review 4 32
· Glossary 33
· Review Answers
The technical term electricity is the property of certain particles to possess a force
field which is neither gravitational nor nuclear. To understand what this means, we
need to start simply.
Everything, from water and air to rocks, plants and animals, is made up of minute
particles called atoms. They are too small to see, even with the most powerful
microscope. Atoms consist of even smaller particles called protons, neutrons
and electrons. The nucleus of the atom contains protons, which have a positive
charge, and neutrons, which have no charge. Electrons have a negative charge and
orbit around the nucleus. An atom can be compared to a solar system, with the
nucleus being the sun and the electrons being planets in orbit.
Electrons can be freed from their orbit by applying an external force, such as
movement through a magnetic field, heat, friction, or a chemical reaction.
A free electron leaves a void, which can be filled by an electron forced out of its
orbit from another atom. As free electrons move from one atom to another, an
electron flow is produced. This electron flow is the basis of electricity.
The cliché, “opposites attract,” is certainly true when dealing with electrical charges.
Charged bodies have an invisible electrical field around them. When two likecharged
bodies are brought close together, they repel each other. When two unlike
charged bodies are brought closer together, their electrical fields work to attract.
When we look at the flow of electricity, we need to look at its characteristics. There
are three main characteristics of electricity:
Despite the fact that it has been positively determined that electron flow is the
correct theory, the conventional flow theory still dominates the industry. Either
theory can be used as long as the orientations are correct. Conventional flow will be
used from this point on in these training modules unless otherwise stated.
Voltage is the force that is applied to a conductor to free electrons, which causes
electrical current to flow. It is measured in volts or “V”. Current will flow in a
conductor as long as voltage, the electrical pressure, is applied to the conductor.
Voltage is expressed in a number of ways: