1 the nature of electricity all mater is composed of atoms atoms are made up of: protons [ + ]...

1

The Nature of ElectricityThe Nature of Electricity

All Mater is Composed of Atoms

All Mater is Composed of Atoms

Atoms are made up of:

Protons [ + ]

Neutrons

Electrons [ - ]

2

Atomic StructureAtomic Structure

• Protons and Neutrons form the Nucleus

• Electrons Orbit the nucleus

• Electrons are arraigned in Shells

• Protons and Neutrons form the Nucleus

• Electrons Orbit the nucleus

• Electrons are arraigned in Shells

3

Electrical ChargeElectrical Charge

• Protons have a Positive electrical charge

• Neutrons have no electrical charge

• Electrons have a Negative electrical charge

• Protons have a Positive electrical charge

• Neutrons have no electrical charge

• Electrons have a Negative electrical charge

4

The law of Attraction & RepulsionThe law of Attraction & Repulsion

• Like charges repel

• Opposite charges attract

• Like charges repel

• Opposite charges attract

5

Electrons Orbit the NucleusElectrons Orbit the Nucleus

• Electrons are always in motion • They move at the speed of light• The centrifugal force produced by their orbit

around the nucleus prevents contact between the protons and electrons

• Electrons are always in motion • They move at the speed of light• The centrifugal force produced by their orbit

around the nucleus prevents contact between the protons and electrons

-

6There is normally one electron for every proton in the nucleus

There is normally one electron for every proton in the nucleus

• The number of protons in the nucleus determines the type of Atom [element]

• Hydrogen is the simplest Atom – it has 1 proton and 1 electron

• The number of protons in the nucleus determines the type of Atom [element]

• Hydrogen is the simplest Atom – it has 1 proton and 1 electron

7

CarbonCarbon

• 6 Protons

• 6 Neutrons

• 6 Electrons

• 6 Protons

• 6 Neutrons

• 6 Electrons

8

Electron ShellsElectron Shells

• First Shell – 2 Electrons

• Second Shell – 8 Electrons

• Third Shell – 4 Electrons




• The electrons orbiting the nucleus are arranged in a series of shell or layers

Silicon 14 Protons, 14 Electrons

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Electron Shells [2]Electron Shells [2]

Copper – 29 Protons & 29 Electrons




• Fourth Shell – 1 Electron

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Conductors and InsulatorsConductors and Insulators

• The electrical properties of an element are determined by the number of electrons in the outermost shell

• The electrical properties of an element are determined by the number of electrons in the outermost shell

If there are less than 4 electrons in the outermost shell the element will conduct electricity - a conductor

If there are more than 4 electrons in the outermost shell the element will not conduct electricity - an insulator

If there are exactly 4 electrons in the outermost shell the element will not conduct electricity sometimes – a semi-conductor

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Loose ElectronsLoose Electrons

• When there are 3 or fewer electrons in the outer shell the electrons are not tightly bound to the nucleus

• A stray electron can easily knock one of the electrons out

• When there are 3 or fewer electrons in the outer shell the electrons are not tightly bound to the nucleus

• A stray electron can easily knock one of the electrons out

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Electron MotionElectron Motion

• Electrons are set in motion by energy from:

– Light– Heat– Chemical reaction– Magnetism

• Electrons are set in motion by energy from:

– Light– Heat– Chemical reaction– Magnetism

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Loose electrons can jumpfrom atom to atomLoose electrons can jumpfrom atom to atom

• Loose electrons can easily jump from one atom to another

• Loose electrons can easily jump from one atom to another

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Electron CurrentElectron Current

• When Conductor atoms are tightly packed together a loose electron will knock on of the electrons out of orbit

• That electron will be repelled away from its original atom and knock loose an electron on a neighboring atom

• When Conductor atoms are tightly packed together a loose electron will knock on of the electrons out of orbit

• That electron will be repelled away from its original atom and knock loose an electron on a neighboring atom

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Electrical CurrentElectrical Current

• The movement of electrons from atom to atom is called an electrical current

• The term current flow is applied to the movement of electrons through a conductor

• The movement of electrons from atom to atom is called an electrical current

• The term current flow is applied to the movement of electrons through a conductor

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Metals are excellent conductors of electricityMetals are excellent conductors of electricity

• Elements with 3 or fewer electrons in their outermost shell are classified as metals

• The best conductors of electric currents are:

– Silver– Aluminum– Copper– Iron– Gold– Graphite [Carbon]

• Elements with 3 or fewer electrons in their outermost shell are classified as metals

• The best conductors of electric currents are:

– Silver– Aluminum– Copper– Iron– Gold– Graphite [Carbon]

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InsulatorsInsulators

• Elements with more than 4 electrons in their outer shells and chemical compounds are poor conductors of electrons

• Materials that do not conduct electricity are called Insulators

• Glass, rubber [not containing carbon black] and plastics are generally good insulators

• Elements with more than 4 electrons in their outer shells and chemical compounds are poor conductors of electrons

• Materials that do not conduct electricity are called Insulators

• Glass, rubber [not containing carbon black] and plastics are generally good insulators

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Chemical compoundsChemical compounds

• Chemical compounds – molecules made up of two or more different elements – such as iron oxide [iron and oxygen] are generally very poor conductors.

• When iron turns into rust it becomes electrically non-conductive

• Chemical compounds – molecules made up of two or more different elements – such as iron oxide [iron and oxygen] are generally very poor conductors.

• When iron turns into rust it becomes electrically non-conductive

Iron atom Oxygen

atom

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VoltageVoltage

• The amount of force that sets electrons in motion is called VOLTAGE

• Voltage is the equivalent of PRESSURE in a hydraulic system

• Voltage may also be called “electro motive force” [ EMF ]

• The amount of force that sets electrons in motion is called VOLTAGE

• Voltage is the equivalent of PRESSURE in a hydraulic system

• Voltage may also be called “electro motive force” [ EMF ]

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AmperesAmperes

• The volume of electrons passing through a conductor is called AMPERS

• AMPERS are the total number of electrons moving through a conductor in a given amount of time

• In a hydraulic system the equivalent of amperes would be gallons per minute

• The volume of electrons passing through a conductor is called AMPERS

• AMPERS are the total number of electrons moving through a conductor in a given amount of time

• In a hydraulic system the equivalent of amperes would be gallons per minute

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Electrical CircuitsElectrical Circuits

• To make electricity useful an electric circuit is needed

• To make electricity useful an electric circuit is needed

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Parts of electrical circuitsParts of electrical circuits

Every electric circuit must have:

Every electric circuit must have:

A Source of electron voltage

An electrical Load

Conductor wires

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Current SourceCurrent Source

• When the engine is running the vehicles generator [alternator] is the source of electrical voltage for the vehicle

• When the engine is running the vehicles generator [alternator] is the source of electrical voltage for the vehicle

• During starting and when the engine is not running the battery is the source of voltage for the vehicle

• During starting and when the engine is not running the battery is the source of voltage for the vehicle

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LoadLoad

• The Load is the work done by an electric circuit

• Typical automotive circuit loads are:

• The Load is the work done by an electric circuit

• Typical automotive circuit loads are:

Electric MotorsSolenoidsLight BulbsHeating Elements

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Conductor WiresConductor Wires

• Automotive electrical systems use multi-stranded copper wire covered with plastic insulation.

• Multi-strand wire allows the wires to flex as the vehicle goes over bumps in the road surface.

• The wire is coated with vinyl insulation that prevents shorting between wires and any other component the wires may contact.

• Automotive electrical systems use multi-stranded copper wire covered with plastic insulation.

• Multi-strand wire allows the wires to flex as the vehicle goes over bumps in the road surface.

• The wire is coated with vinyl insulation that prevents shorting between wires and any other component the wires may contact.

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Chassis groundChassis ground

• The metal of the vehicle’s body, engine and transmission serves as a return path for electrical current back to the battery.

• This pathway through the body and engine is called ‘ground’.

• Since the engine and transmission are supported on rubber mounts a ground cable or ‘ground strap’ is needed to electrically connect them to the body.

• The metal of the vehicle’s body, engine and transmission serves as a return path for electrical current back to the battery.

• This pathway through the body and engine is called ‘ground’.

• Since the engine and transmission are supported on rubber mounts a ground cable or ‘ground strap’ is needed to electrically connect them to the body.

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Body groundBody ground

• The negative battery cable is typically bolted directly to the body directly below the battery tray.

• The negative battery cable is typically bolted directly to the body directly below the battery tray.

Rubber sub-frame

mounts

Rubber engine mounts

Body ground bolt

Negative battery cable

Engine ground cable

+ -

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Body groundBody ground

• The engine ground strap normally shares this connection to the body

• In this configuration the battery negative terminal, engine block and vehicle body are all electrically connected

• The engine ground strap normally shares this connection to the body

• In this configuration the battery negative terminal, engine block and vehicle body are all electrically connected

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Positive ground vs. negative groundPositive ground vs. negative ground

• Many automobiles built before 1968 had positive ground electrical systems.

• After 1968 manufactures standardized on the more common negative ground system when alternators were introduced in the early 1960’s.

• There is no significant performance difference between positive ground and negative ground systems – obviously the generator, electric motors and vehicle electronics must be constructed differently and cannot be interchanged

• Many automobiles built before 1968 had positive ground electrical systems.

• After 1968 manufactures standardized on the more common negative ground system when alternators were introduced in the early 1960’s.

• There is no significant performance difference between positive ground and negative ground systems – obviously the generator, electric motors and vehicle electronics must be constructed differently and cannot be interchanged

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Electron Theory of CurrentElectron Theory of Current

• Electrons, since they are negatively charged travel from the negative battery terminal – through the load – then returns to the positive battery terminal.

• Electrons, since they are negatively charged travel from the negative battery terminal – through the load – then returns to the positive battery terminal.

+-

• The flow of electrical current is in the opposite direction of electron flow – electrical current is said to flow from positive to negative.

• The flow of electrical current is in the opposite direction of electron flow – electrical current is said to flow from positive to negative.

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Conventional Theory of CurrentConventional Theory of Current• Although we now know electrons actually flow from

negative to positive for the first 150 years of electrical technology engineers assumed that electrical current flowed from the positive terminal of the battery – through the load – then returned to the negative battery terminal.

• Although we now know electrons actually flow from negative to positive for the first 150 years of electrical technology engineers assumed that electrical current flowed from the positive terminal of the battery – through the load – then returned to the negative battery terminal.

+-

• Whenever we talk about electrical current flow its understood that we mean from positive to negative.

• Whenever we talk about electrical current flow its understood that we mean from positive to negative.

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Properties of electrical circuitsProperties of electrical circuits

• Every electrical circuit has 3 electrical properties:

• Every electrical circuit has 3 electrical properties:

VOLTAGE

AMPERS

RESISTANCE

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Voltage Voltage

• Voltage is the electrical pressure that pushes electrons through a circuit

• Higher voltage levels push more electrons through a circuit – resulting in more Amperes of current Flow

• The unit of measure is the Volt

• Voltage is measured with a voltmeter

• The symbol for volts is the letter V

• Voltage is the electrical pressure that pushes electrons through a circuit

• Higher voltage levels push more electrons through a circuit – resulting in more Amperes of current Flow

• The unit of measure is the Volt

• Voltage is measured with a voltmeter

• The symbol for volts is the letter V

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AmperageAmperage

• Amperage is the total volume of electrons that pass through a circuit in a given amount of time

• Amperage is normally limited by the resistance of the circuit load

• The unit of Amperage is AMPS• Amperage is measured with a ammeter• The term CURRENT is synonymous with

amperage

• Amperage is the total volume of electrons that pass through a circuit in a given amount of time

• Amperage is normally limited by the resistance of the circuit load

• The unit of Amperage is AMPS• Amperage is measured with a ammeter• The term CURRENT is synonymous with

amperage

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ResistanceResistance

• Resistance is the opposition to the flow of electrical current

• The LOAD is the principle resistance in an electrical circuit

• Increased resistance cause a decrease in electrical current flow

• Resistance is the opposition to the flow of electrical current

• The LOAD is the principle resistance in an electrical circuit

• Increased resistance cause a decrease in electrical current flow

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• The unit of resistance is the OHM

• The symbol for Ohms is the Greek letter omega [ ]

• Resistance is measured with an ohmmeter

• The unit of resistance is the OHM

• The symbol for Ohms is the Greek letter omega [ ]

• Resistance is measured with an ohmmeter

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• Factors that effect the resistance of a conductor• Factors that effect the resistance of a conductor

Chemical Properties of the ConductorSize of the conductorLength of the conductorTemperature of the conductorMagnetism

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Unwanted ResistanceUnwanted Resistance

• Corrosion in the conductor or terminal ends• Loose electrical connections• Conductor wires too small for the current

being carried• Excessive conductor length

• Corrosion in the conductor or terminal ends• Loose electrical connections• Conductor wires too small for the current

being carried• Excessive conductor length

Unwanted resistance can caused by:Unwanted resistance can caused by:

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Resistive loads – heating elementsResistive loads – heating elements

• Electrical resistance is often used to generate heat

• Electrical heating elements are made of materials that are relative poor conductors

• Automotive applications for heating elements:

• Heated rear windows• Heated seats• Glow plugs in Diesel engines• Heated outside rear view mirrors• Heated oxygen sensors• Supplemental heat for hybrid and electrical vehicle

HVAC systems

• Electrical resistance is often used to generate heat

• Electrical heating elements are made of materials that are relative poor conductors

• Automotive applications for heating elements:

• Heated rear windows• Heated seats• Glow plugs in Diesel engines• Heated outside rear view mirrors• Heated oxygen sensors• Supplemental heat for hybrid and electrical vehicle

HVAC systems

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Resistive loads – motor speed controlResistive loads – motor speed control

• Resistors can also be used to limit the amount of current [amps] that pass through a circuit.




• Stepped resistors are used to control the speed of the heater fan motor.

• Three small coils of wire with varying amounts of resistance allow the fan speed to be set for low, medium, medium-high.

• Stepped resistors are used to control the speed of the heater fan motor.

• Three small coils of wire with varying amounts of resistance allow the fan speed to be set for low, medium, medium-high.

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Resistive loads – light bulbsResistive loads – light bulbs

• A light bulb is a resistance that generates so much heat that it glows white hot.

• Light bulbs have a resistance wire made of tungsten called a ‘filament’ that operates at temperatures above 5000 deg. F.

• Tungsten won’t melt at 5000 degrees but it will react with the oxygen in the air and burn.

• A light bulb is a resistance that generates so much heat that it glows white hot.

• Light bulbs have a resistance wire made of tungsten called a ‘filament’ that operates at temperatures above 5000 deg. F.

• Tungsten won’t melt at 5000 degrees but it will react with the oxygen in the air and burn.

• To prevent oxidation of the filament it is surrounded by an inert gas, typically argon inside a sealed glass envelope.

• To prevent oxidation of the filament it is surrounded by an inert gas, typically argon inside a sealed glass envelope.

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Schematic symbols for basic electrical circuits

Schematic symbols for basic electrical circuits

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Conductor wiresConductor wires

• Conductor wires are represented by solid lines• There in no electrical connection where wires cross

unless there is a dot at the intersection

• Conductor wires are represented by solid lines• There in no electrical connection where wires cross

unless there is a dot at the intersection

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Conductor wiresConductor wires

• A dot at the intersection of two wires indicates a splice

• The electrical path after a splice divides into several branches

• A dot at the intersection of two wires indicates a splice

• The electrical path after a splice divides into several branches

Splice

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Electrical symbol for groundElectrical symbol for ground

• DIN = ‘Deutsches Institut für Normung’ or ‘German Institute for Standardization’.

• DIN symbols are found on wiring schematics for all European vehicles and late model vehicles manufactured by General Motors

• DIN = ‘Deutsches Institut für Normung’ or ‘German Institute for Standardization’.

• DIN symbols are found on wiring schematics for all European vehicles and late model vehicles manufactured by General Motors

Traditional DIN

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Electrical symbol for batteriesElectrical symbol for batteries

Single cell Multi cell

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Electrical symbol for fixed resistorsElectrical symbol for fixed resistors

Traditional DIN

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Electrical symbol for light bulbsElectrical symbol for light bulbs

Traditional DIN

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How voltage, amperage and resistance work

together in a simple electrical circuit

How voltage, amperage and resistance work

together in a simple electrical circuit

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Ohm’s LawOhm’s Law

• The relationship between volts, amps and ohms is expressed in a simple mathematical formula called Ohm’s law

• The relationship between volts, amps and ohms is expressed in a simple mathematical formula called Ohm’s law

I = ----ER

I - Amperes

E - Voltage

R - Ohms

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Ohm’s LawOhm’s Law

• Two additional formulas can be derived from Ohm’s law

• Two additional formulas can be derived from Ohm’s law

I = ----ER

R = ----EI

E = I x R

To calculate Amps

To calculate Ohms

To calculate Volts

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Ohm’s Law – current calculationOhm’s Law – current calculation

• A simple circuit that has a 12 volt source and a 2 ohm load will have 6 amps of current passing through it.

• A simple circuit that has a 12 volt source and a 2 ohm load will have 6 amps of current passing through it.

2 Ohm12 Volt 2 Ohm

+

--

=ER

I

=122

6< - Current flow = 6 amps

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• If the load resistance is doubled to 4 ohms the current passing through the circuit will be cut in half to 3 amps.

• If the load resistance is doubled to 4 ohms the current passing through the circuit will be cut in half to 3 amps.

2 Ohm12 Volt 4 Ohm

+

--

=ER

I

=124


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• If we cut the resistance down to 1 ohm the current passing through the circuit will increase to 12 amps.

• If we cut the resistance down to 1 ohm the current passing through the circuit will increase to 12 amps.

2 Ohm12 Volt 1 Ohm

+

--

=ER

I

=121


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Current vs. resistanceCurrent vs. resistance

• As resistance increases the amount of current [amps] flowing through the circuit decreases proportionally

• Adding resistance to a circuit provides a method of regulating the flow of current

• When a circuit is not working at its maximum potential look for excessive resistance somewhere in the circuit

• As resistance increases the amount of current [amps] flowing through the circuit decreases proportionally

• Adding resistance to a circuit provides a method of regulating the flow of current

• When a circuit is not working at its maximum potential look for excessive resistance somewhere in the circuit

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Voltage and currentVoltage and current

• If we change the voltage source from 12 volts to 6 volts and the resistance remains unchanged the amount of current passing through a circuit will be cut in half.

• If we change the voltage source from 12 volts to 6 volts and the resistance remains unchanged the amount of current passing through a circuit will be cut in half.

2 Ohm6 Volt 2 Ohm

+

--

=ER

I

=62


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• If we double the voltage source from 12 volts to 24 volts and the resistance remains unchanged the amount of current passing through a circuit also be doubled.

• If we double the voltage source from 12 volts to 24 volts and the resistance remains unchanged the amount of current passing through a circuit also be doubled.

2 Ohm24 Volt 2 Ohm

+

--

=ER

I

=242


Voltage and currentVoltage and current

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• If we know the voltage of a circuit 12 volts and we measure the current flowing through the circuit as 2 amps we can calculate the resistance using Ohm’s law.

• If we know the voltage of a circuit 12 volts and we measure the current flowing through the circuit as 2 amps we can calculate the resistance using Ohm’s law.

2 Ohm12 Volt ? Ohm

+

-- =242

12Actual current = 2 amps

Calculating resistanceCalculating resistance

R =EI

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• If the voltage is 24 volts and we measure the current flow at 6 amps the resistance will be 4 ohms.

• If the voltage is 24 volts and we measure the current flow at 6 amps the resistance will be 4 ohms.

2 Ohm24 Volt ? Ohm

+

-- =246

4Actual current = 6 amps

Calculating resistanceCalculating resistance

R =EI

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• If we know the resistance and the desired current we can calculate the voltage required using Ohm’s law.

• If we know the resistance and the desired current we can calculate the voltage required using Ohm’s law.

2 Ohm? Volts 6 Ohm

+

--

Desired current = 6 amps

Calculating voltageCalculating voltage

E = I x R

6 x 6 = 36

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Voltage vs. resistanceVoltage vs. resistance

• If the resistance of a circuit is doubled it will take twice as much voltage to push the same number of amps through the circuit

• If the resistance of a circuit is doubled it will take twice as much voltage to push the same number of amps through the circuit

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• How many amps are passing through this circuit ..?

• How many amps are passing through this circuit ..?

9 Volts 6 Ohm

+

-

Problem #1Problem #1

I=E/R9 volts / 6 ohms =1.5

amps

I=E/R9 volts / 6 ohms =1.5

amps

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• How many volts are needed to push 3 amps through this circuit ..?

• How many volts are needed to push 3 amps through this circuit ..?

? Volts 6 Ohm

+

-


V=E x R6 ohms x 3 amps = 18

volts

V=E x R6 ohms x 3 amps = 18

volts

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• If there are 2 amps of current flowing through this circuit what is the resistance ..?

• If there are 2 amps of current flowing through this circuit what is the resistance ..?

9 Volts ? Ohm

+

-


R=E x I9 volts / 2 amps = 4.5

ohms

R=E x I9 volts / 2 amps = 4.5

ohms

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Alternating CurrentAlternating Current

• Household appliances utilize alternating current [AC]

• Household current changes polarity 60 times a second [60 Hertz]

• Electrons flowing through an AC circuit reverse direction of flow 120 times each second

• Household appliances utilize alternating current [AC]

• Household current changes polarity 60 times a second [60 Hertz]

• Electrons flowing through an AC circuit reverse direction of flow 120 times each second

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AC CurrentAC Current

• Household current switches from positive to negative and back again 60 times each second.

• Household current switches from positive to negative and back again 60 times each second.

1/60th of a second

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AC CurrentAC Current

• AC current is used for household appliances because it can be easily transformed from one voltage level to another

• DC [Direct Current] used in automobiles cannot be transformed to any other voltage level without first converting it to AC current

• An inverter is used to convert DC into AC current

• AC current is used for household appliances because it can be easily transformed from one voltage level to another

• DC [Direct Current] used in automobiles cannot be transformed to any other voltage level without first converting it to AC current

• An inverter is used to convert DC into AC current

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Circuit terminology

Circuit terminology

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Closed CircuitClosed Circuit

• An electrical circuit that has a complete path from source - to load – back to the source is called a closed circuit

• An electrical circuit that has a complete path from source - to load – back to the source is called a closed circuit

+-

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Closed CircuitClosed Circuit

• When a switch is turned on it is closed and electrical power can flow through the circuit.

• An on/off switch has two positions; open and closed

• When a switch is turned on it is closed and electrical power can flow through the circuit.

• An on/off switch has two positions; open and closed

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Open CircuitOpen Circuit

• An electrical circuit that has a broken path – due to a disconnected wire, switch turned off or a defective component is called a open circuit

• An electrical circuit that has a broken path – due to a disconnected wire, switch turned off or a defective component is called a open circuit

+-

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Open CircuitOpen Circuit

• A switch that is in the turned off position is said to be open

• Anything that interrupts the flow of current through a circuit is called an open

• Disconnected wires, blown fuses and disconnected electrical connectors cause an open condition

• A switch that is in the turned off position is said to be open

• Anything that interrupts the flow of current through a circuit is called an open

• Disconnected wires, blown fuses and disconnected electrical connectors cause an open condition

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Short CircuitShort Circuit

• When the current path is allowed to bypass the load it is called a short circuit

• When the current path is allowed to bypass the load it is called a short circuit

+-

• Short circuits are very dangerous as they will cause the wires to overheat – igniting fires and generating toxic

smoke

Short Circuit

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Short Circuit – fire hazardsShort Circuit – fire hazards

• Short circuits are what causes fuses to blow or circuit breakers to trip

• Without a fuse or other circuit protection device a short circuit would set the vehicle on fire

• When there is a short the absence of the load resistance that normally limits the current flow through the circuit the wires will get hot enough to melt their insulation and set the vehicle interior or engine compartment on fire

• Short circuits are what causes fuses to blow or circuit breakers to trip

• Without a fuse or other circuit protection device a short circuit would set the vehicle on fire

• When there is a short the absence of the load resistance that normally limits the current flow through the circuit the wires will get hot enough to melt their insulation and set the vehicle interior or engine compartment on fire

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Short Circuit - toxic gasShort Circuit - toxic gas

• Besides the fire hazard, when the insulation on the wires burns it produces toxic gasses that will make driving the vehicle impossible

• Imagine what would it would be like if you were driving a car at 70 mph when the wiring inside the cabin caught fire

• Besides the fire hazard, when the insulation on the wires burns it produces toxic gasses that will make driving the vehicle impossible

• Imagine what would it would be like if you were driving a car at 70 mph when the wiring inside the cabin caught fire

1 the nature of electricity all mater is composed of atoms atoms are made up of: protons [ + ]...

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