Chapter 7 Basic Automotive Electricity Seabee-Books Pdf

Chapter 7 Basic Automotive Electricity Seabee
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This course map shows all of the chapters in Construction Mechanic Basic The. suggested training order begins at the bottom and proceeds up Skill levels increase as. you advance on the course map, Automotive Chassis and Body. Construction Equipment Power Trains C, Drive Lines Differentials Drive Axles M. and Power Train Accessories, Automotive Clutches Transmissions. and Transaxles, Hydraulic and Pneumatic Systems, Automotive Electrical Circuits and B. Basic Automotive Electricity S, Cooling and Lubrication Systems I.
Diesel Fuel Systems C, Gasoline Fuel Systems, Construction of an Internal Combustion. Principles of an Internal Combustion, Technical Administration. Features of this Manual, This manual has several features which make it easy to use online. Figure and table numbers in the text are italicized The figure or table is either. next to or below the text that refers to it, The first time a glossary term appears in the text it is bold and italicized When. your cursor crosses over that word or phrase a popup box displays with the. appropriate definition, Audio and video clips are included in the text with italicized instructions telling.
you where to click to activate it, Review questions that apply to a section are listed under the Test Your. Knowledge banner at the end of the section Select the answer you choose If the. answer is correct you will be taken to the next section heading If the answer is. incorrect you will be taken to the area in the chapter where the information is for. NAVEDTRA 14264A 7 2, review When you have completed your review select anywhere in that area to. return to the review question Try to answer the question again. Review questions are included at the end of this chapter Select the answer you. choose If the answer is correct you will be taken to the next question If the. answer is incorrect you will be taken to the area in the chapter where the. information is for review When you have completed your review select. anywhere in that area to return to the review question Try to answer the question. NAVEDTRA 14264A 7 3, 1 0 0 BASIC PRINCIPLES of ELECTRICITY. All activity 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. 1 1 0 Composition of Matter, All matter regardless of its state solids liquids and gases is made up of tiny particles. known as atoms Atoms combine in small groups of two or more to form molecules. however when atoms are divided smaller particles are created These particles have. positive or negative electrical charges, There are just over 100 different basic materials in the universe and millions of different.
compounds can be formed from them These basic materials are called elements Iron. 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 one electron circles Figure 7 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 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 is whirled in a circle in the air, The centrifugal force exerted tries to move. the ball out of its circular path but is, balanced by the string the attractive force. Figure 7 1 Hydrogen atom, 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. NAVEDTRA 14264A 7 4, 1 2 0 Composition of Electricity. When there are more than two electrons in, an atom they move about the nucleus in. different orbits which are referred to as, shells Figure 7 2 The innermost shells of.
the atom contain electrons that are not, easily freed and are referred to as bound. electrons The outermost shell contains what, is referred to as free electrons These free. electrons differ from bound electrons in that, they can be moved readily from their orbit. If a point that has an excess of electrons, negative is connected to a point that has a. shortage of electrons positive a flow of, electrons electrical current will flow through.
the connector conductor until an equal, amount of electrical charge exists between Figure 7 2 Composition of an. the two points atom, 1 3 0 Electron Theory of Electricity. A charge of electricity is formed when numerous electrons break free of their atoms and. gather in one area When the electrons begin to move in one direction as along a wire. for example the effect is a flow of electricity or an electric current Actually electric. generators and batteries could be called electron pumps because they remove. electrons from one part of an electric circuit and concentrate them in another part of the. circuit For example a generator takes electrons away from the positive terminal and. concentrates them at the negative terminal Because the electrons repel each other like. electrical charges repel the electrons push out through the circuit and flow to the. positive terminal unlike electrical charges attract Thus we can see that an electric. current is actually a flow of electrons from a negative terminal to a positive terminal. Test your Knowledge Select the Correct Response, 1 All matter is made up of tiny particles known by what term. B Electrons, C Neutrons, 2 0 0 ELECTRIC CURRENT, It has been proved that electrons negative charges move through a conductor in. response to an electric field Electric current is defined as the directed flow of. electrons and the direction of electron movement is from a region of negative potential. to a region of positive potential Therefore electric current can be said to flow from. negative to positive, NAVEDTRA 14264A 7 5, 2 1 0 Conductors.
Any material that will allow an electrical, current to flow through it is an electrical. conductor Conductors are used in, automotive equipment to carry electric. current to all of the electrical equipment The, electrical properties of a substance depend. mainly on the number of electrons in the, outermost shell of each atom The maximum. number of electrons in an outer shell is eight, When there are less than four electrons in.
the outer shell of an atom these electrons, will tend to be free This condition allows the. free motion of electrons making the, substance a conductor Figure 7 3. Electrical energy is transferred through Figure 7 3 Conductors. conductors by means of the movement of, free electrons that migrate from atom to atom within the conductor Each electron. moves a short distance to the neighboring atom where it replaces one or more electrons. by forcing them out of their orbits The replaced electrons repeat this process in nearby. atoms until the movement is transmitted throughout the entire length of the conductor. thus creating a current flow Copper is an example of a good conductor because it has. only one free electron This electron is not held very strongly in its orbit and can break. away from the nucleus very easily Silver is a better conductor of electricity but it is too. expensive to be used in any great quantity Because of this copper is the conductor. used most widely in automotive applications, 2 2 0 Insulators. Any material that blocks electrical current, flow is an electrical insulator Insulators.
also are necessary to keep the electric, current from taking a shorter route instead. of going to the intended component, Whenever there are more than four. electrons in the outer orbits of the atoms of, a substance these electrons will tend to be. bound causing restriction of free electron, movement making it an insulator Figure 7. 4 Common insulating substances in, automotive applications are rubber plastic.
and fiberboard, Figure 7 4 Insulators, NAVEDTRA 14264A 7 6. 2 3 0 Semiconductors, A semiconductor is an electrical device that acts as a conductor under certain. conditions and as a nonconductor under other conditions The most popular of all. semiconductors is silicon In its pure state silicon is neither a good conductor nor. insulator But by processing silicon in certain ways its conductive or insulative. properties can be adjusted to suit just about any need When a number of silicon atoms. are jammed together in crystalline glasslike form they form a covalent sharing bond. Therefore the electrons in the outer ring of one silicon atom join with the outer ring of. other silicon atoms resulting in a sharing of outer ring electrons between all of the. atoms Figure 7 5 shows that covalent sharing gives each atom eight electrons in its. Figure 7 5 Covalent bonding of silicon, outer orbit making the orbit complete This makes the material an insulator because it. contains more than four electrons in its outer orbit When certain materials such as. phosphorus are added to the silicon crystal in highly controlled amounts the resultant. mixture becomes a conductor Figure 7 6 This is because phosphorus which has five. electrons in forming a covalent bond with silicon which has four electrons in its outer. shell will yield one free electron per molecule thus making the material an electrical. conductor The process of adding impurities to a semiconductor is called doping Any. semiconductor material that is doped to yield free electrons is called N type material. Figure 7 6 Phosphorus doped silicon, NAVEDTRA 14264A 7 7. When boron which has three electrons in its outer ring is used to dope the silicon. crystal the resultant covalent bonding yields seven electrons in the outer shell This. leaves an opening for another electron Figure 7 7 This space is called a hole and can. Figure 7 7 Boron doped silicon, be considered a positive charge just as the extra electrons that exist in N type.
semiconductor material are considered a negative charge Materials that have holes in. their outermost electron shells are called positive or P type materials To understand the. behavior of P type semiconductors it is necessary to look upon the hole as a positive. current carrier just as the free electron in N type semiconductors are considered. negative current carriers Just as electrons move through N type semiconductors holes. move from atom to atom in P type semiconductors Movement of holes through P type. semiconductors however is from the positive terminal to the negative terminal For this. reason any circuit analysis of solid state circuitry is done on the basis of positive to. negative conventional current flow, When a source voltage such as a battery is connected to N type material an electric. current will flow through it Figure 7 8 The current flow in the N type semiconductor. consists of the movement of free electrons the same as the current flow through a. natural conductor such as copper When a current source of sufficient voltage is. connected across a P type material an electric current will also flow through it but any. current flow in a P type semiconductor is looked upon as the movement of positively. charged holes The holes appear to move toward the negative terminal as the electrons. Figure 7 8 Hole movement theory, NAVEDTRA 14264A 7 8. enter the material at the negative terminal fill the holes and then move from hole to. hole toward the positive terminal As is the case with the N type semiconductors the. movement of electrons through P type semiconductors toward the positive terminal is. motivated by the natural attraction of unlike charges. 2 3 1 Diodes, A diode is a device that will allow current to pass through itself in only one direction. Figure 7 9 A diode can be thought of as an electrical check valve Diodes are. constructed by joining N type material and P type material together The negative. electrical terminal is located on the N type material and the positive terminal is located. on the P type material, Figure 7 9 Diode operation. When a diode is placed in a circuit the N material is connected to the negative side of. Knowing the basic principles of automotive electricity is essential for 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

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