1. ELECTRICITY

2. SYMBOLS We have looked at several different symbols
We will be using many of them from now on so get used to them

3. Conductors Materials that allow electricity to flow easily thru it
Material made up of atoms with the valance ring (outer) with 1, 2, or 3 electrons
Most metals

4. Insulators
Materials that don’t’ allow electricity to flow easily thru it
Material made up of atoms with the valance ring with 5, 6, 7, or 8 electrons
Air
Glass
Paper
Wood

5. Semi Conductors
Materials that are not good conductors or good insulators
Material made up of atoms with the valance ring with 4 electrons
Carbon (C)
Silicon (Si)

6. Electricity The flow of electrons How do we get electrons to flow?
Electrons being held
In orbit by the attraction
Of the protons

7. Two copper atoms side by side

8. Two copper atoms side by side

9. Electrons bouncing around in random drift in the wire
Copper wire
Made up of billions of copper atoms
Electrons bouncing around in
random drift in the wire
Remember the wire is full of electrons at
Random drift.

10. Atoms loosing or gaining electrons
All atoms have an equal number of protons and electrons
When an atom looses one electron it becomes a Positive Ion
It is now unstable and wants an electron back to become stable
When an atom gains an electron it becomes a Negative Ion
It is now unstable and wants to get rid of an electron to become stable

11. Shortage of electrons here Extra Electrons here Now the electrons that
were at random drift are
in a directed drift
Extra Electrons here

12. Voltage
Electrical pressure (pushes current) Atoms that are short electrons and atoms with extra electrons
Unit of measure is the volt
Measured with a voltmeter
Note! A good voltmeter won’t
have any flow thru it

13. Ways to make voltage Magnets Chemical Pressure Heat Light Friction
Most common

14. Current
The directed movement of electrons or the flow. (pushed by voltage)
Unit of measure is the amp or ampere
Measured with an ammeter or amp meter

15. How much is one amp?
One amp is 6.25 X 10 to the 18th power of electrons past a given point per second. (one Coulomb)
6,250,000,000,000,000,000

16. Conventional theory Says that current flows from + to -
Scientists first guessed that it was the proton
that was in motion in the atom

17. Electron theory Says that current flows from – to +
When scientists discovered that it was the electron
that was in motion, electron theory was born

18. Does it matter?
When talking about electronics, it does matter which way current flows, but for basic electricity, it doesn’t
Most automotive texts, and classes still teach conventional theory, so that is what we will stick with.

19. Resistance
Opposition to current flow (anything that slows down current)
Unit of measure is the ohm
Measured with an ohmmeter

20. Factors that affect the resistance of a circuit
Type of material used
Conductor / Insulator / Semi-conductor
Length of the circuit
Diameter of the circuit
Temperature
Connections

21. Wire diameter AWG Gauge size Metric Millimeters squared
American Wire Gauge
Metric
Millimeters squared

22. 36
0.005
0000
0.500

23. Elements of a Circuit (must have)
Nice to have

24. One wire circuits

25. OHM’S LAW
When the voltage and resistance are equal in a circuit, ONE amp will flow (Saunders version)
One volt will push one amp through one ohm of resistance
A picture is worth a
thousand words

26. Ohms Law
Current flow is strictly a result of how much voltage and resistance there is
To get more current
Increase voltage
Decrease resistance
Or both
To get less current to flow
Decrease voltage
Increase resistance

27. Ohm’s law formulas Voltage is represented by the letter “E”
Amperage is represented by “I”
Resistance is represented by “R”
E = I x R

28. Here is an easier way to remember
The three formulas
Need to know
Need to know

29. When you know the amperage and resistance of a circuit you can figure
the voltage
Voltage = amperage times resistance

30. When you know the voltage and amperage of a circuit you can figure
the resistance
Resistance = voltage divided by amperage

31. When you know the voltage and resistance of a circuit you can figure
the amperage
Amperage = voltage divided by resistance

32. D.C Challenge Let’s apply what we have learned
Ohms law
We will also learn about electrical power or watts
Power is the rate of doing _________
Watts are the amount of electrical work
There will be an ohm’s law and power quiz after D.C. Challenge

33. ELECTRICITY
After ATECH 1-7

34. Must know! Series Circuit Rules Only one path Amperage stays the same
Each resistance adds up to the total
R1+R2=Rt
Voltage divided between the loads (all used up or dropped)

35. Voltmeters Hooked across or in parallel
Red to most positive and black to most negative
Used in a live circuit

36. Ammeters Hooked in series (in line and part of the circuit)
Red to most positive and black to most negative
Used in a live circuit
Be careful not to hook
across voltage (it will
blow fuse

37. Ohm Meters Used in a dead circuit Must be hooked across or in parallel
Analog meter must be calibrated to compensate for battery
Part you want to measure must be isolated from the rest of the circuit
Good connections

38. Type of circuits
Atech 8-11
Atech
12-14
Atech 1-7

39. ATECH 7-11
Parallel circuits
The rules are going to change

40. Lets go get it done!

41. ELECTRICITY

42. Problem Circuits

43. Open Circuit No flow Infinite resistance Won’t use circuit protection
Meters to find open
Volt (will read source voltage across open)
Ohm (will read infinite across open)

44. High resistance Less flow than normal Won’t use circuit protection
Meters to find
Voltmeter (will drop more voltage at problem)
Ohmmeter (will read more resistance at problem)

45. Short circuit More flow than normal May use circuit protection
Meters to use
Ohmmeter (less resistance at problem)
Voltmeter (only if circuit is still live, voltmeter will read less voltage drop at problem)

46. Grounded circuit (short to ground, dead short)
Huge flow (no resistance)
Will use circuit protection or burn up circuit
Ohmmeter is the only meter to use (circuit will be dead)
Ohmmeter will show no resistance to ground at the problem

47. Short to voltage Hardest to find and fix
When one circuit shorts voltage into another

48. Low voltage Won’t use circuit protection Less amps will flow Caused by
Bad battery
Charging system fault

52. Circuit Protection

54. D.C. Current
Current always flowing the same way

55. A.C. Current
Current flows first one way, then the other

56. Type of circuits