Basics. Student booklet

Transcription

1 Basics Student booklet

2

3 Basics - INDEX :32 Basics This module deals with many basic facts about how an electric current is created and about how an atom is constructed. It also deals with materials used in Volvo trucks. The trucks today are full will electrical equipment and it is for that reason very important to have knowledge about how electrical circuits and components work. This module will motivate you to find out more about what is really happening inside modern trucks. Contents The importance of electricity Electrical systems Materials used in trucks The Atom Electrical charges Electrical current Heat and magnetism Conductors Insulators Sum up Assessment INDEX -

4

5 Basics - BasElbasics01.swf :31 The importance of electricity After seeing bundles of wires the size of Arnold Schwartzeneggar's biceps in a typical modern truck and trying to read diagrams that make a Tokyo street map look simple, you may find it hard to believe that the earliest trucks had no electrical whatsoever. Then, motor vehicles were truly mechanical devices. Driver controls Today's trucks have many functions that demand various electrical components and systems in order to work. To fault-trace and repair these components and systems it is important to understand the basics of electricity. The driver can control many of these functions electrically. This helps to increase safety and comfort. Internal and external lighting, for example headlamps and indicators, can be activated. Driver and passenger seat positions can be adjusted. The position of the door mirrors can be adjusted. Side windows can be raised and lowered. The wiper and washer can be turned on and off. 1

6 Basics - BasElbasics02.swf :31 Electrical systems More complicated electrical systems consist of control units, which calculate and control different functions. The control units receive information from various electrical sensors. The SRS (Supplementary Restraint System) continuously calculates when and if airbags and seat belt tensioners should be activated. The ESP (Electronic Stability Program) continuously calculates the driving state of the truck to find out if it approaches the limits of stability. If so, it activates the brake on one or more wheels to stabilise the truck. The EMS (Engine Management System) controls the fuel injection to regulate injected fuel volume and injection timing. This makes it possible to achieve low fuel consumption and a minimum of noise and exhaust emissions. The VECU (Vehicle Electronic Control Unit) is the central unit in the electronic system. It collects data from various sensors and systems and transmits this data to the other control units. The LCM (Light Control Module) controls all lighting in the truck. Also, it checks the status of the lighting circuits when the driver turns the ignition key to the driving position, and protects the lighting circuits from excessive current. 2

7 Basics - BasElbasics03.swf :31 Materials used in trucks Trucks are constructed from many different materials. Different types of material have different applications depending on their physical, chemical and electrical characteristics. Steel can withstand a great deal of stress and is relatively cheap to manufacture and to process. Because of this steel is used in the truck's bodywork for example. Glass is manufactured in different ways depending on its application. The windscreen of a truck is usually laminated to be strong enough to withstand stone chips, while the side and rear windows are often hardened. There are a wide variety of plastics. Plastic is used internally and externally on the truck. Plastic is durable, easy to shape and relatively inexpensive. Aluminium is a low-weight material with great resistance to corrosion. However, it is expensive to produce and can only be used for purposes where it is absolutely necessary. Many truck parts are made either entirely or partially from aluminium, for example rims, body components, front and rear suspension components, engine and transmission. Rubber has different characteristics depending on its application. The mouldings between door and frame have to be soft and flexible. The rubber compound in tyres is very important for the tyre's ability to get good traction. 3

8 Basics - BasElbasics04.swf :31 The Atom All materials consist of atoms. There are different kinds of atoms with different physical, chemical and electrical characteristics. Materials consisting of only one type of atom are called elements. There are slightly more than 100 elements. Other materials consist of a mixture of different elements. Atoms consist of a nucleus and a number of electrons. The nucleus is in the centre of the atom. It consists of protons and neutrons. Each of them weigh about 1800 times that of an electron so therefore the weight of the nucleus makes up most of the total weight of the atom. Electrons circle around the nucleus. The weight of the electrons is a very small part of the total weight of the atom. The nucleus consists of protons and neutrons. Protons are located in the nucleus. The weight of a proton is about 1800 times that of an electron. Neutrons are part of the nucleus. The weight of a neutron is about 1800 times that of an electron. 4

9 Basics - BasElbasics05.swf :31 Electrical charges Electrons, neutrons and protons have different characteristics making them act on each other in different ways. These characteristics are called electrical charges. The electron has a negative electrical charge (-). The proton has a positive electrical charge (+). Neutrons are charged neutrally (0), i.e. they have no charge. Particles with different charges are attracted to one another, while particles with the same charge repel one another. Negatively charged electrons are attracted to the positively charged nucleus. The positively charged protons in the nucleus are so tightly bound to one another by the internal forces of the nucleus, that they are not able to repel one another. Normally an atom consists of an equal number of electrons and protons, which means that its overall charge is neutral. The number of neutrons varies depending on the material, but it does not affect the total charge of the atom. 5

10 Basics - BasElbasics06.swf :31 Electron orbits Electrons move in orbits at different distances from the nucleus. Each orbit can hold a certain maximum number of electrons. These orbits are supplied with electrons from further inside the atom. This means that the second orbit does not contain any electrons until the first path is full. The exact number of orbits in an atom depends on how many electrons it has. The aluminium atom has 2 electrons in the first orbit closest to the nucleus. An atom can have a maximum of 2 electrons in this orbit. It has 8 electrons in the second orbit. An atom can have a maximum of 8 electrons in this orbit. It has 3 electrons in the third orbit. An atom can have a maximum of 18 electrons in this orbit. Electrical current The three outermost electrons are loosely bound to the atom. This is due to their distance from the nucleus and the effect on them from the inner electrons. In the right circumstances these electrons can leave the atom and transfer to another atom. During this transfer they are known as free electrons. When free electrons move in one direction this is called an electrical current. 6

11 Basics - BasElbasics07.swf :31 Heat and magnetism When an electrical current flows through a cable it produces heat energy. Heat energy is used to heat the rear windshield, the door mirrors and the seats for example. Filaments in light bulbs use heat energy to create light. When an electrical current flows through a cable a magnetic field is created around the cable. The greater the current the stronger the magnetic field. Magnetic fields are used for many different things such as opening and closing contacts in relays. Magnetic fields are also used in more complex components such as ignition coils, injector valves and electrical motors. 7

12 Basics - BasElbasics08.swf :31 Conductors The ability to conduct electricity depends on how strongly the electrons are bound to the atom. The fewer the electrons in the outer path and the further away they are from the nucleus, the looser is their bond to the nucleus. In some materials the outer electrons are so loosely bound that they can leave their path and move about freely in the material. Such types of material are called conductors. Many conductors consist of only one element. Metals are generally very good conductors. In the automotive industry, conductors are used for conducting electrical currents. The conductor used depends on its capacity to conduct electricity and its ability to resist corrosion. Copper has excellent conductivity and is also very corrosion resistant. One use for copper is in electrical wiring. Tin is not as conductive but is very corrosion resistant. Tin is used as surface layer in most connectors. Steel consists of a mixture of different materials and iron is one of these. Steel is not such a good conductor and its resistance to corrosion is limited, but it is cheap and mechanically very durable. Steel is used in the trucks framework. 8

13 Basics - BasElbasics09.swf :31 Insulators The more electrons there are in the outer path, the tighter these electrons are bound to the atom. In some materials the outer electrons are so tightly bound that they cannot leave their path and move about freely in the material. Such types of material are called insulators. Insulators are usually made from a mixture of different elements. The automotive industry uses insulators to prevent electrical currents being conducted. Insulators used depend on the environment and application. Plastic is flexible and is used as an insulator and as a casing for cables. The plastic protects wires and prevents the electrical current leaking. Plastic is made from several different elements such as carbon and hydrogen. 9

14 Basics - BasElbasicssumup18.swf :31 Sum up This sum up is to be used as a discussion forum of what we have gone through in this module. If there are some questions you can discuss these in the group. Questions to discuss: What kind of material do we use in our trucks today? What kind of characteristics do these have? What functions can the driver control by himself? What kind of electrical systems do we have in the trucks today? Give examples! What parts does an Atom consist of? What is an electrical charge? What is an electrical current? Why do heat and magnetism arise? What is the difference between insulators and conductors? 10

15 Basics - BasElbasicsassess19.swf :32 Assessment 1. What is generated when a current runs through a conductor? 2. What is an electrical current? 3. What is a good conductor? 4. Which three particles are all atoms constructed of? 5. Which of the three particles in the atom is the source to electric current? 11

16

17

18 Copyright 2006 Volvo Truck Corporation