1. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 15 Basics of Electrical Systems

2. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Basics of Electricity Provides power for lights, TVs, stereos, and other household items Basis for communication between our brain and the rest of our body Cannot be seen, the effects can be seen, felt, heard, and smelled

3. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Flow of Electricity Electricity is the flow of electrons from one atom to another Energy is released as electrons move

4. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Flow of Electricity (Cont.) Electrons have a negative charge Attracted to a positive charge When an electron leaves, the atom has a positive charge

5. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Flow of Electricity (Cont.) An electrical power source provides a more positive charge Supplies free electrons to maintain the continuous flow of electricity

6. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Flow of Electricity (Cont.) To have continuous flow of electricity: – Must be an excess of electrons in one place – Must be a lack of electrons in another place – Must be a path between the two places

7. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Flow of Electricity (Cont.) Automobiles use two power sources Battery – Uses chemical energy to provide energy – Produces direct current electricity AC Generator – Moves magnetic field passed a conductor – Produces alternating current

8. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electrical Terms Current Flow – Amperes – Measured in amps Electrical Pressure – Voltage – Measured in volts Resistance – Measured in ohms

9. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Amperage or Current DC current – flows in one direction only AC current – electrons change direction at a fixed rate Automobiles typically use DC Some components generate or use AC

10. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage Electrical pressure The force developed by the attraction of the electrons and protons The more positive one side of a circuit is, the more voltage is present Voltage does not flow Also called electromotive force (EMF)

11. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage

12. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Resistance When any substance flows, it meets resistance Resistance to electron flow can be measured Resistance produces heat Loads are good resistance Too low or too high resistance can cause circuit faults

13. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

14. Alternating Current Constantly changes in voltage and direction DC voltage from a battery is fixed AC voltage appears as a sine wave Changes in amplitude (strength) and direction Highest positive and negative points are called peak-to-peak value

15. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

16. Alternating Current (Cont.) Since AC does not have a constant value, less heat is produced than DC One amp AC equals the equivalent heat produced by one amp DC The effective value of AC is equal to 0.707 times its peak value AC can be applied in phases

17. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

18. Knowledge Check What are the three main electrical units?

19. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuit Terminology Complete circuits provide a path that connects the positive and negative A complete circuit is called a closed circuit An incomplete circuit is an open circuit Electrical flow can be controlled and perform work in a closed circuit

20. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Closed Circuit

21. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Open Circuit

22. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuit Terminology (Cont.) Components that use electrical power put a load on the circuit and consume energy These components are called loads The amount of current that flows in a circuit is determined by the resistance of the circuit The energy used is measured in volts

23. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Grounding the Load Most automobiles use the chassis as a ground conductor Current passes from the battery, through the load, through the metal frame, and back to the battery Engine and transmission are grounded to the chassis

24. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

25. Power Source – Battery or alternator Conductor – Wires Load – Light bulb, motor, solenoid, etc. Control Device – Switches, relays Protection Device – Fuse, circuit breaker, fuse link Circuit Components

26. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuit Components (Cont.)

27. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. 1 volt can push 1 ampere through 1 ohm of resistance The formula can be expressed as: – E (volts) = I (amps) x R (resistance) – R (resistance) = E (volts) / I (amps) – I (amps) = E (volts) / R (resistance) Ohm’s Law Formula

28. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

29. Using Ohm’s Law

30. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using Ohm’s Law (Cont.) Since E = I · R 12V = 4A · 3Ω 3Ω = 12V / 4A 4A = 12V / 3Ω

31. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Which of the following is correct? A. E = I/R B. R = I/E C. E = I x R D. I = R/E

32. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage Drops The amount of voltage required to cause current flow through a load Energy (voltage) is changed to another form as it flows through a load

33. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. The voltage leaving the load is less than the voltage supplied – the difference is the voltage drop Dependent upon current and resistance Voltage Drops (Cont.)

34. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Voltage Drop

35. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage Drops (Cont.) Calculated using Ohm’s law Voltage drop is equal to the circuit current times the loads resistance

36. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage Drops (Cont.) If only one load in circuit, the voltage drop will equal circuit voltage More than one load in a circuit, the voltage drop will vary with the resistance of the loads

37. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage Drops (Cont.) One Load = Full voltage dropped Two Loads = Each uses some of the voltage

38. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. AC Circuits Resistance in AC circuits called impedance Impedance (Z) is measured in Ohms Defined as the operating resistance of a load Additional opposition to current flow results in interaction of magnetic fields in the conductor Voltage drop = I · Z

39. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Power and Watt’s Law Watt’s law calculates the power used by a load Watts represents the rate at which electrical energy is converted into another form, such as light, heat, or motion

40. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Power and Watt’s Law (Cont.) With equal voltage, a load with a lower resistance will use more power than a load with a higher resistance A 40W bulb has higher resistance than a 100W bulb

41. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuits Resistance must be low enough to allow the available voltage to push electrons between two points A complete circuit must have an unbroken path for current to flow

42. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuits (Cont.) Most circuits have five basic parts: – Power and ground sources – Conductors – Loads – Controllers – Circuit protection devices

43. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuits (Cont.) There are three basic types of circuits: – Series circuits – Parallel circuits – Series-parallel circuits Each has its own characteristics regarding amperage, voltage, and resistance

44. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. The current is the same at all points of the circuit The voltage drop across each resistor will be different if the resistor values are different The sum of the voltage drops across each resistor equals the source voltage The total resistance is equal to the sum of all the resistances Characteristics of a Series Circuit

45. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Series Circuit

46. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

47. The total resistance will always be less than the smallest resistor lowest resistance leg The voltage drop across each parallel leg will be the same The voltage applied to each leg is the same Characteristics of a Parallel Circuit

48. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. The current flow through each leg will be different if the resistances are different The sum of the current in each leg equals the total current of the parallel circuit Characteristics of a Parallel Circuit (Cont.)

49. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Parallel Circuit

50. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Each leg has 12V supply 12V dropped by each load/leg

51. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using Ohm’s Law Resistances not added in parallel circuits For a two leg circuits: – R total = R1 x R2/R1 + R2 For multiple leg circuits:

52. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. The total resistance is the sum of the resistance value of the parallel portion and the series resistance The voltage drop over the parallel branch resistance is determined by the resistance value of the series resistor Characteristics of a Series-Parallel Circuit

53. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. The total amperage of each parallel branch is determined by the resistance in the branch Total circuit amperage is determined by resistance of the parallel and the series resistance Characteristics of a Series-Parallel Circuit (Cont.)

54. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Series-Parallel Circuit

55. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

56. Kirchhoff’s Law “Voltage Law” describes series circuits – The sum of the voltage drops equals the voltage applied “Current Law” describes parallel circuits – At any junction point in a circuit, the current arriving is equal to the current leaving

57. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Voltage Law Example

58. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Current Law Example

59. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check What are the five components of a complete circuit?

60. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuit Components Power Sources Modern vehicles use 12-volt systems Battery voltage is 12.6 volts Charging system output 14 – 15 volts Increasing voltage reduces amperage for the same resistance – A higher voltage supply requires smaller wire due to decreased current flow

61. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Power Sources (Cont.) Modern vehicles have increased power demands Current charging system produces 800 to 1500 watts Near future demand will be 3000 – 7000W

62. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Resistors Fixed resistors – Have only one rating and do not change Tapped or stepped resistors – Are usually used to control motor speeds

63. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Resistors (Cont.) Rheostats – Have two wires and are used to regulate current

64. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Resistors (Cont.) Potentiometers – Have three wires and act as voltage divider

65. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Resistors (Cont.) Temperature variable resistor called a thermistor Used to determine coolant and air temperatures

66. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Thermistors Negative temperature coefficient (NTC) and positive temperature coefficient (PTC) – NTC resistance decreases with increasing temp

67. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuses – Contain a metal strip designed to melt at a specific current rating Three basic types: – Glass cartridge – Ceramic – Blade - most common in modern vehicles Types of Circuit Protection

68. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuse Types

69. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fusible Links – Are special wires that are designed to melt when circuit current exceeds a given level Maxi-fuses – Take the place of fusible links – Are used to protect several circuits Types of Circuit Protection (Cont.)

70. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Circuit Breaker – Is designed to open when circuit current exceeds a given point – Most will reset when current flow stops PTC Circuit Protector – Its resistance increases when current rises above a specific level Types of Circuit Protection (Cont.)

71. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Typical Fuse/Relay Box

72. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. High Voltage Systems Require special circuit protection devices The service plug contains a high-amp fuse

73. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Can be normally open (NO) or normally closed (NC) Simplest form is a single pole, single throw (SPST) Some have one input and two outputs (SPDT) Can have several inputs and/or several outputs (ganged switch) Switches

74. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Relays Uses a small current circuit to control a larger current circuit Uses an electromagnetic switch to open or close contacts that control the larger current Can be normally open or normally closed

75. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Typical Relay

76. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. A solenoid is an electromechanical device that operates similarly to a relay Solenoids are used to do mechanical work such as switching: – Electrical circuits – Vacuum circuits – Liquid circuits Solenoids

77. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Starter Solenoid

78. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Technician A says relays are a form of circuit protection device. Technician B says solenoids use electromagnetism to operate. Who is correct?

79. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Conductors and Insulators Conductors have low resistance to current flow Four or fewer electrons in outer shell or ring Most metals are conductors Insulators resist current flow More than four electrons in outer shell or ring Thermal plastics most common

80. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Conductors and Insulators (Cont.)

81. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Conductors and Insulators (Cont.) Conductor resistance depends on: – Length of wire – Diameter of wire – Temperature of wire Double wire length – double the resistance Double wire diameter – halve the resistance Increase wire temperature – increase resistance

82. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wires Solid Wires – Single strand conductors Stranded Wires – Most common

83. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wires (Cont.) Size standards established by SAE – Called American Wire Gauge (AWG) 0 – 40 – 0 is largest – 40 is smallest

84. © 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Printed Circuits Rigid or flexible printed circuit boards used in dash panel displays Light sockets plug into board Connects many circuits in a small space