1. Automobile Theories of Operation
Chapter Seven
Automobile Theories of Operation

2. Objectives
Discuss theories of physics in designing and operating vehicles
Discuss first two laws of thermodynamics and their application in an engine
Define energy and the two types of energy

3. Objectives Discuss how pressure and vacuum help operate the engine
Discuss Newton’s three Laws of Motion
Define electricity, voltage, current, and resistance
Discuss magnetism

4. Objectives Name types of electrical circuits
Discuss use of hydraulics in vehicles
Discuss other factors in designing and operating a vehicle
Discuss horsepower and torque

5. Introduction Automobile is made up of eight major interactive systems
Power to the vehicle and components
Comfort and protect the passenger

6. Thermodynamics Study of using radiant heat to perform mechanical work
First Law
Energy cannot be created or destroyed

7. Thermodynamics Second Law In a perfect heat engine
Heat produced would be completely converted to mechanical work

8. Energy and Work
Energy is the capacity of matter to perform work through its motion or position
Work is a unit of energy and may be measured in foot-pounds (ft-lbs.)

10. Pressure and Vacuum
Pressure is amount of force used to hold a gas or liquid in place
Atmospheric pressure can be used to achieve work in a vehicle or components

11. Pressure and Vacuum Vacuum is pressure below atmospheric pressure
Automotive systems use these principles to operate

12. Newton’s Laws of Motion
First Law
An object at rest tends to stay at rest
An object in motion tends to stay in motion
Second Law
A moving object will travel in a straight line and in one direction

13. Newton’s Laws of Motion
Third Law
For every action there is an equal and opposite reaction

14. Electrical Theory, Measuring, and Circuits
George Simon Ohm
One volt to push one ampere of current through one ohm of resistance
Conductors
Natural elements to move electrical current
Only one electron in valence ring
Best conductor is copper

15. Electrical Theory, Measuring, and Circuits
Voltage
Electrons are moved by voltage
Voltage is Electromotive Force (EMF)
Electron theory

16. Electrical Theory, Measuring, and Circuits
Current
Amount of moving electrons expressed in an understandable term
Most automotive systems are relatively low amperage

18. Electrical Theory, Measuring, and Circuits
Resistance
Anything that uses voltage
Nonconductive elements are resistant and classified as insulators
Corrosion can cause resistance
Unintentional resistance can disrupt circuit operation

19. Electrical Theory, Measuring, and Circuits
Magnetism
Created any time current is flowing
Number of windings and how they are insulated from one another affects magnetic field strength
Magnetic fields can be used to create electricity

20. Electrical Theory, Measuring, and Circuits
Electrical Measurements
Instruments are necessary to allow control of electricity
Ohm’s Law can calculate whether a circuit is operating properly

21. Electrical Theory, Measuring, and Circuits
Path electricity follows from negative to positive side
Can work with a power source, conductor, and load

23. Electrical Theory, Measuring, and Circuits
Series Circuits
Provide one path for current to travel
Defect in circuit will affect entire circuit
Generally not used in automotive applications
True series circuit is the starter circuit

24. Electrical Theory, Measuring, and Circuits
Parallel Circuits
Provide more than one path to ground
Common in automotive applications
One failed component will not affect entire circuit
Typical circuit
Exterior lighting

25. Electrical Theory, Measuring, and Circuits
Series-Parallel Circuits
Most common circuit in automotive applications
Series portion controls parallel portion
Typical circuit
Headlamp circuit

26. Electrical Theory, Measuring, and Circuits
Circuit Protection
Protect circuits from overload situations
Designed to protect other circuits and even the whole vehicle
Fuses melt at preset amperage amounts
Circuit breakers are similar to fuses, but can be reset instead of replaced

28. Electrical Theory, Measuring, and Circuits
Circuit Defects
Open
Circuit is incomplete and current can’t flow
Short-to-Ground
Two conductors have worn through insulation
Results in a switch turning on more than its designed circuit

29. Electrical Theory, Measuring, and Circuits
Circuit Defects
Short-to-Ground
Unintentional connection between a feed conductor and ground

30. Electrical Service Information
Wiring Diagram
Paper- or computer-based diagrams
Various circuits and devices
Most show wire colors and wire sizes
Newer systems may also have diagrams
Component Locators
List items and their locations in vehicle

32. Hydraulic Theory
Pressure in a closed hydraulic circuit will be the same everywhere in the circuit
Hydraulic circuits are similar to electrical circuits

33. Hydraulic Theory Three measures in hydraulic circuits
Force, pressure, area
Hydraulic fluids selected on type of system in use and work being performed

36. Vehicle Design Aerodynamics Study of how an object moves through air
Can affect performance and fuel mileage

37. Vehicle Design Passenger Protection
Seat belts and air bags are designed to protect the passenger in an accident
Crumple zones have been added to absorb impact forces

39. Vehicle Design Materials
Must be selected to provide specific performance in applications
Gaskets must be able to work with different materials on either side

40. Vehicle Design Horsepower versus Torque Horsepower is speed
Torque is pulling

41. Working Around Supplemental Restraint Systems (SRS)
Caution must be exercised when working around SRS systems
Disconnect power any time you are working around the system

42. Working Around Supplemental Restraint Systems (SRS)
Never probe connectors with powered test lights
Serious injury or death can result from neglecting safety precautions

43. Diagnostic Steps Six Steps to Follow Confirm customer’s complaint
Collect vehicle data
Collect vehicle TSB, recalls, or other information
Test system
Determine and complete repair
Test repair

44. Summary
Newton Laws
Volts, ohms, and amperes are electrical measurements
Measurements of hydraulics are force, area, and pressure
Vehicle design is limited by available materials and technology