BASIC AUTOMOTIVE ELECTRICITY INTRODUCTION
Learning Objective: Describe the basic principles of electrical and magnetic theory. Identify the materials, the devices, and the different types of electrical circuits. Determine electrical measurements using Ohm's law.
The basic principles of automotive electricity are the essential knowledge required by the mechanic to understand the operation of all-automotive electrical systems and components. Unless you have a clear understanding of these fundamental principles, you will find it difficult to service the various electrical components and systems encountered in the Naval Construction Force (NCF). This understanding will enable you to make sound decisions in the troubleshooting process of all electrical systems.
BASIC PRINCIPLES OF ELECTRICITY
All activity that takes place in any type of electrical circuit depends on the behavior of tiny electrical charges, called electrons. To understand the behavior of electrons, we must investigate the composition of matter. The electron is one of the basic electrical components of all matter.
COMPOSITION OF MATTER
There are over 100 different basic materials in the universe. These basic materials are called elements. Iron is one element; copper, aluminum, oxygen, hydrogen, and mercury are examples of elements. The basic particles that make up all the elements, and thus the entire universe, are called protons, electrons, and neutrons. A proton is the basic particle having a single positive charge; therefore, a group of protons produces a positive electrical charge. An electron is the basic particle having a single negative charge; therefore, a group of electrons produces a negative electrical charge. A neutron is the basic particle having no charge; therefore, a group of neutrons would have no charge.
The construction of atoms of the various elements can be examined starting with the simplest of all- hydrogen. The atom of hydrogen consists of one proton, around which is circling one electron (fig. 1-1). There is an attraction between the two particles, because negative and positive electrical charges always attract each other. Opposing the attraction between the two particles, and thus preventing the
Figure 1-1.- Composition of matter.
electron from moving into the proton, is the centrifugal force on the electron caused by its circular path around the proton. This same sort of balance is produced if a ball tied to string was whirled in a circle in the air. The centrifugal force exerted tries to move the ball out of its circular path and is balanced by the string (the attractive force). If the string should break, the centrifugal force would cause the ball to fly away. Actually, this is what happens at times with atoms. The attractive force between the electron and proton sometimes is not great enough to hold the electron in its circular path and the electron breaks away.
In an atom, unlike electrical charges attract and like electrical charges repel each other. Electrons repel electrons and protons repel protons, except when neutrons are present. Though neutrons have no electrical charge, they do have the ability to cancel out the repelling forces between protons in an atomic nucleus and thus hold the nucleus together.