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## ELECTRICITY

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**We have looked at several different symbols**We will be using many of them from now on so get used to them SYMBOLS**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 Conductors**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 Insulators**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) Semi Conductors**The flow of electrons**How do we get electrons to flow? Electricity Electrons being held In orbit by the attraction Of the protons**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.**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 Atoms loosing or gaining electrons**Shortage of**electrons here Now the electrons that were at random drift are in a directed drift Extra Electrons here**Electrical pressure (pushes current) Atoms that are short**electrons and atoms with extra electrons Voltage • Unit of measure is the volt • Measured with a voltmeter Note!A good voltmeter won’t have any flow thru it**Magnets**Chemical Pressure Heat Light Friction Most common Ways to make voltage**The directed movement of electrons or the flow. (pushed by**voltage) Current • Unit of measure is the amp or ampere • Measured with an ammeter or amp meter**One amp is 6.25 X 10 to the 18th power of electrons past a**given point per second. (one Coulomb) How much is one amp? 6,250,000,000,000,000,000**Conventional theory**Says that current flows from + to - Scientists first guessed that it was the proton that was in motion in the atom**Electron theory**Says that current flows from – to + When scientists discovered that it was the electron that was in motion, electron theory was born**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. Does it matter?**Opposition to current flow (anything that slows down**current) Resistance • Unit of measure is the ohm • Measured with an ohmmeter**Type of material used**Conductor / Insulator / Semi-conductor Length of the circuit Diameter of the circuit Temperature Connections Factors that affect the resistance of a circuit**AWG Gauge size**American Wire Gauge Metric Millimeters squared Wire diameter**0.005**36 0000 0.500**Elements of a Circuit (must have)**Nice to have**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 OHM’S LAW A picture is worth a thousand words**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 Or both Ohms Law**Voltage is represented by the letter “E”**Amperage is represented by “I” Resistance is represented by “R” Ohm’s law formulas E = I x R**Here is an easier way to remember**The three formulas Need to know Need to know**When you know the amperage and**resistance of a circuit you can figure the voltage Voltage = amperage times resistance**When you know the voltage and**amperage of a circuit you can figure the resistance Resistance = voltage divided by amperage**When you know the voltage and**resistance of a circuit you can figure the amperage Amperage = voltage divided by resistance**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 D.C Challenge**ELECTRICITY**After ATECH 1-7**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) Series Circuit Rules Must know!**Hooked across or in parallel**Red to most positive and black to most negative Used in a live circuit Voltmeters**Hooked in series (in line and part of the circuit)**Red to most positive and black to most negative Used in a live circuit Ammeters Be careful not to hook across voltage (it will blow fuse**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 Ohm Meters**Atech 8-11**Atech 12-14 Type of circuits Atech 1-7**Parallel circuits**The rules are going to change ATECH 7-11**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) Open Circuit**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) High resistance**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) Short circuit**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 Grounded circuit(short to ground, dead short)**Hardest to find and fix**When one circuit shorts voltage into another Short to voltage**Won’t use circuit protection**Less amps will flow Caused by Bad battery Charging system fault Low voltage