AUT 242 Automotive Electricity II

1. AUT 242Automotive Electricity II Chapter 3, Fundamentals

2. OBJECTIVES After studying Chapter 3, the reader should be able to: • Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A” (General Electrical/Electronic System Diagnosis). • Define electricity. • Explain the units of electrical measurement. • Discuss the relationship among volts, amperes, and ohms. • Explain how magnetism is used in automotive applications.

3. ELECTRICITY • Our universe is composed of matter, which is anything that has mass and occupies space. • The smallest particle that an element can be broken into and still retain the properties of that element is known as an atom. • Electricity is the movement of electrons from one atom to another.

4. In an atom (left), electrons orbit protons in the nucleus just as planets orbit the sun in our solar system (right). ELECTRICITY

5. ELECTRICITYPositive and Negative Charges • The parts of the atom have different charges. • The orbiting electrons are negatively charged, while the protons are positively charged. • Neutrons have no charge at all.

6. ELECTRICITYPositive and Negative Charges • In a normal, or balanced, atom, the number of negative particles equals the number of positive particles. • The number of neutrons varies according to the type of atom.

7. ELECTRICITYPositive and Negative Charges • The positive and negative charges within an atom are like the north and south poles of a magnet. • Charges that are alike will repel each other, similar to the poles of a magnet. • Charges that are not alike will attract one another.

8. ELECTRICITYPositive and Negative Charges • When an atom is not balanced, it becomes a charged particle called an ion. • Ions try to regain their balance of equal protons and electrons by exchanging electrons with neighboring atoms. • An unbalanced, positively charged atom (ion) will attract electrons from neighboring atoms.

9. ELECTRICITYElectron Shells • Electrons orbit around the nucleus in definite paths. • These paths form shells, like concentric rings, around the nucleus. • The hydrogen atom is the simplest atom, with only one proton, one neutron, and one electron. More complex elements contain higher numbers of protons, neutrons, and electrons

10. ELECTRICITYFree and Bound Electrons • The outermost electron shell or ring, called the valence ring, is the most important to our study of electricity. • When the valence ring has five or more electrons in it, it is fairly full. • The electrons are held tightly, and it is hard for a drifting electron to push its way into the valence ring.

11. ELECTRICITYFree and Bound Electrons • These tightly held electrons are called bound electrons. • As the number of electrons increases, they occupy increasing energy levels that are further from the center of the atom.

12. ELECTRICITYFree and Bound Electrons Electrons in the outer orbit, or shell, can often be drawn away from the atom and become free electrons.

13. ELECTRICITYConductors • Conductors are materials with fewer than four electrons in their atom’s outer orbit. • Silver, copper, gold, aluminum, tungsten, zinc, brass, platinum iron, nickel, tin, steel & lead are some examples. • A conductor is any element that has one to three electrons in its outer orbit.

14. Copper is an excellent conductor of electricity because it has just one electron in its outer orbit, making it easy to be knocked out of its orbit and flow to other nearby atoms. This causes electron flow, which is the definition of electricity. ELECTRICITYConductors

15. ELECTRICITYInsulators • Insulators are materials with more than four electrons in their atom’s outer orbit. • Plastics, wood, rubber, glass, ceramics and insulating varnish are common examples.

16. ELECTRICITYSemiconductors • Materials with exactly four electrons in their outer orbit are neither conductors nor insulators and are called semiconductor materials. • Geranium, silicone, carbon • Diodes, transistors, computer chips.

17. ELECTRICITYHow Electrons Move Through a Conductor • If an outside source of power, such as a battery, is connected to the ends of a conductor, a positive charge (lack of electrons) is placed on one end of the conductor and a negative charge is placed on the opposite end of the conductor. • Current electricity is the movement of electrons through a conductor.

18. ELECTRICITYConventional Theory versus Electron Theory • It was once thought that electricity had only one charge and moved from positive to negative. • The discovery of the electron and its negative charge led to the electron theory, which states that there is electron flow from negative to positive.

19. Conventional theory states that current flows through a circuit from positive (+) to negative (-). Automotive electricity uses the conventional theory in all electrical diagrams and schematics. ELECTRICITYConventional Theory versus Electron Theory

20. ELECTRICITYAmperes • The ampere is the unit used throughout the world to measure current flow. • One ampere is the movement of 1 coulomb (6.28 billion billion electrons) past a point in 1 second.

21. ELECTRICITYAmperes • Amperes are measured by an ammeter (not ampmeter). • An ammeter is installed in the path of the electrons similar to a water meter used to measure the flow of water in gallons per minute. The ammeter displays current flow in amperes.

22. ELECTRICITYVolts • The volt is the unit of measurement for electrical pressure. • Voltage is also called electrical potential, because if there is voltage present in a conductor, there is a potential (possibility) for current flow • Voltage is the electrical pressure that causes the electrons to flow through a conductor.

23. This digital multimeter set to read DC volts is being used to test the voltage of a vehicle battery. Most multimeters can also measure resistance (ohms) and current flow (amperes). ELECTRICITYVolts

24. ELECTRICITYOhms • Resistance to the flow of current through a conductor is measured in units called ohms. • The resistance to the flow of free electrons through a conductor results from the countless collisions the electrons cause within the atoms of the conductor. FIGURE 3-19 Resistance to the flow of electrons through a conductor is measured in ohms.

25. ELECTRICITYWatts • A watt is the electrical unit for power, the capacity to do work. • A display at the Henry Ford Museum in Dearborn, Michigan, that includes a hand-cranked generator and a series of light bulbs. This figure shows a young man attempting to light as many bulbs as possible. The crank gets harder to turn as more bulbs light because it requires more power to produce the necessary watts of electricity.

26. SOURCES OF ELECTRICITYFriction • When certain different materials are rubbed together, the friction causes electrons to be transformed from one to the other. • Static Electricity – the charge is static and does not move. • Tires on pavement; rubber shoes on a carpet or helecopter rotor blades are all capable of producing static charges. • May interfere with electronic equipment.

27. SOURCES OF ELECTRICITYHeat • When pieces of two metals are joined together at both ends and one junction is heated, current passes through the metals. • This junction is called a thermocouple • Often used for temperature sensing devices. FIGURE 3-21 Electron flow is produced by heating the connection of two different metals.

28. SOURCES OF ELECTRICITYLight • When certain metals are exposed to light, some of the light energy is transferred to the free electrons of the metal. • This is called photoelectricity. • Often used for light sensors for devices like headlight dimmers and photo light meters. FIGURE 3-22 Electron flow is produced by light striking a light-sensitive material.

29. SOURCES OF ELECTRICITYPressure • When subjected to pressure, certain crystals, such as quartz, develop a potential difference, or voltage, on the crystal faces. • Called piezoelectricity. • One example, used as a knock sensor for engine timing.

30. SOURCES OF ELECTRICITYChemistry • Two different materials (usually metals) placed in a conducting and reactive chemical solution create a difference in potential, or voltage, between them. • This principle is called electrochemistry and is the basis of the automotive battery.

31. SOURCES OF ELECTRICITYConductors and Resistance • All conductors have some resistance to current flow. Several principles of conductors and their resistance include the following: • If the conductor length is doubled, its resistance doubles. • If the conductor diameter is increased, its resistance is reduced. • As the temperature increases, the resistance of the conductor also increases.. • Materials used in the conductor have an impact on its resistance.

32. SOURCES OF ELECTRICITYConductors and Resistance

33. SOURCES OF ELECTRICITYResistors • Resistance is the opposition to current flow. • Most electrical and electronic devices use resistors of specific values to limit and control the flow of current. • Two major type of resistor are • Fixed resistors • Variable Resistors.

34. SOURCES OF ELECTRICITYResistors (Fixed Resistor) FIGURE 3-24 A resistor color code interpretation.

35. Fixed Resistor Color Code Chart

36. A typical carbon resistor. SOURCES OF ELECTRICITYResistors

37. SOURCES OF ELECTRICITYVariable Resistors • Two commonly used types • Potentiometers: • 3 wire • are most commonly used as throttle position (TP) sensors on computer-equipped engines. • Rheostat • 2 wire • Heater control, dimming etc.

38. SOURCES OF ELECTRICITYVariable Resistors A three-wire variable resistor is called a potentiometer. A two-wire variable resistor is called a rheostat.

39. SUMMARY • Electricity is the movement of electrons from one atom to another. • Automotive electricity uses the conventional theory that electricity flows from positive to negative. • The ampere is the measure of the amount of current flow. Voltage is the unit of electrical pressure. • The ohm is the unit of electrical resistance. • Sources of electricity include friction, heat, light, pressure, and chemistry

40. REVIEW QUESTIONS • Define electricity. • Electricity is the movement of electrons from one atom to another. • Define ampere, volt, and ohm. • Amp = electron flow • Volt = electrical pressure • Ohm = resistance to electrical flow • List three materials that are conductors and three materials that are insulators. • List four sources of electricity.

41. CHAPTER QUIZ • An electrical conductor is an element with _____ electrons in its outer orbit. • Less than 2 • Less than 4 • Exactly 4 • More than 4

42. CHAPTER QUIZ 2. Like charges _____. • Attract • Repel • Neutralize each other • Add

43. CHAPTER QUIZ 3. Carbon and silicon are examples of _____. • Semiconductors • Insulators • Conductors • Photoelectric materials

44. CHAPTER QUIZ 4. Which unit of electricity does the work in a circuit? • Volt • Ampere • Ohm • Coulomb

45. CHAPTER QUIZ 5. As temperature increases _____. • The resistance of a conductor decreases • The resistance of a conductor increases • The resistance of a conductor remains the same • The voltage of the conductor decreases

46. CHAPTER QUIZ 6. The _____ is a unit of electrical pressure. • Coulomb • Volt • Ampere • Ohm

47. CHAPTER QUIZ 7. Technician A says that a two-wire variable resistor is called a rheostat. Technician B says that a three-wire variable resistor is called a potentiometer. Which technician is correct? • Technician A only • Technician B only • Both Technicians A and B • Neither Technician A nor B

48. CHAPTER QUIZ 8. Creating electricity by exerting a force on a crystal is called _____. • Electrochemistry • Piezoelectricity • Thermoelectricity • Photoelectricity

49. CHAPTER QUIZ 9. The fact that a voltage can be created by exerting force on a crystal is used in which type of sensor? • Throttle position (TP) • Manifold absolute pressure (MAP) • Barometric pressure (BARO) • Knock sensor (KS)

50. CHAPTER QUIZ 10. A potentiometer, a three-wire variable resistance, is used in which type of sensor? • Throttle position (TP) • Manifold absolute pressure (MAP) • Barometric pressure (BARO) • Knock sensor (KS)