Electricity

What is electricity? Is the movement of electrons from atom to atom. Some substances have atoms that allow electrical flow, others do not. Conductors Insulators Is the movement of electrons from atom to atom. Some substances have atoms that allow electrical flow, others do not. Conductors Insulators

The Players Conductors Wires and other metal objects have atoms that allow the flow of electricity Copper, gold, aluminum, steel, etc Insulators Resist the flow of electricity They do not contain free electrons Plastic, rubber, glass, ceramic Conductors Wires and other metal objects have atoms that allow the flow of electricity Copper, gold, aluminum, steel, etc Insulators Resist the flow of electricity They do not contain free electrons Plastic, rubber, glass, ceramic

The Players Atoms Basically consists of small particles called: Protons, neutrons and electrons Neg. (-) charged electrons circle around a center of neutrons and pos. (+) charged protons Free electrons Are extra electrons in the orbit of an atom that are not locked to a proton Atoms Basically consists of small particles called: Protons, neutrons and electrons Neg. (-) charged electrons circle around a center of neutrons and pos. (+) charged protons Free electrons Are extra electrons in the orbit of an atom that are not locked to a proton

Atoms and Electrons The maximum number of electrons in the atom’s valence (outer band) varies, but if it is full, it will be a good insulator The valence is filled, it is in a state of equilibrium, and reluctant to give or take an electron from a neighboring atom. The maximum number of electrons in the atom’s valence (outer band) varies, but if it is full, it will be a good insulator The valence is filled, it is in a state of equilibrium, and reluctant to give or take an electron from a neighboring atom.

Atoms and Electrons An atom with 2 or 3 valence electrons are usually good conductors They contribute to and receive electrons from neighboring atoms. Metals such as gold, silver and copper have a single electron in their valence band, and are excellent conductors. An atom with 2 or 3 valence electrons are usually good conductors They contribute to and receive electrons from neighboring atoms. Metals such as gold, silver and copper have a single electron in their valence band, and are excellent conductors.

Conductor atoms CopperSilverGold

Current, Voltage, & Resistance Current is the flow of electrons through a conductor Just as water flows through a garden hose, electrons flow through a wire in a circuit When current flows through a light bulb, the electrons rub against the atoms causing ‘electrical friction’. The friction heats the filament, making it glow. Current is the flow of electrons through a conductor Just as water flows through a garden hose, electrons flow through a wire in a circuit When current flows through a light bulb, the electrons rub against the atoms causing ‘electrical friction’. The friction heats the filament, making it glow.

Current, Voltage, & Resistance 2 Electron Flow theories: Conventional Theory: States that current flows from Positive (+) to Negative (-) Electron Theory: States that current flows from Negative (-) to Positive (+) This is more widely accepted than the ‘Conventional Theory’ Current is abbreviated I 2 Electron Flow theories: Conventional Theory: States that current flows from Positive (+) to Negative (-) Electron Theory: States that current flows from Negative (-) to Positive (+) This is more widely accepted than the ‘Conventional Theory’ Current is abbreviated I

Current, Voltage, & Resistance Voltage is the force, or ‘electron pressure’, that causes electron flow Similar to water pressure in a hose An increase in voltage causes an increase in current A decrease in voltage causes a decrease in current Voltage is abbreviated V or E Voltage is the force, or ‘electron pressure’, that causes electron flow Similar to water pressure in a hose An increase in voltage causes an increase in current A decrease in voltage causes a decrease in current Voltage is abbreviated V or E

Current, Voltage, & Resistance Is the opposition to current flow. Resistance is needed to control the flow of current in a circuit. Circuit resistance can be increased or decreased to control the flow of electricity High resistance reduces current Low resistance increases current Resistance is abbreviated R Is the opposition to current flow. Resistance is needed to control the flow of current in a circuit. Circuit resistance can be increased or decreased to control the flow of electricity High resistance reduces current Low resistance increases current Resistance is abbreviated R

…end of Part 1

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Part 2 Circuits and Terms

A Circuit To have a simple circuit you need 3 things: 1. A Power Source : Battery, alternator, or generator which supplies the electricity for the circuit 2. A Load : An electrical device that uses electricity 3. Conductors : Wires or metal parts that carry the current between the power source and the load To have a simple circuit you need 3 things: 1. A Power Source : Battery, alternator, or generator which supplies the electricity for the circuit 2. A Load : An electrical device that uses electricity 3. Conductors : Wires or metal parts that carry the current between the power source and the load

A Simple Circuit

A Series Circuit Has more than one load connected in one electrical path Closed circuit Open circuit

A Parallel Circuit Has more than one electrical path. Closed circuitOpen circuit

Some Terms Switch: Allows an electrical circuit to be turned on or off Short Circuit: Is a low-resistance connection that results in excessive current flow Fuse: Protects a circuit against damage caused by a short circuit Switch: Allows an electrical circuit to be turned on or off Short Circuit: Is a low-resistance connection that results in excessive current flow Fuse: Protects a circuit against damage caused by a short circuit

Types of Fuses

Fuses… When a fuse blows, the link in the fuse will melt and burn in half to stop the excess current Fusible Link: Small section of wire designed o burn in half when excess current is detected Circuit Breaker: Performs the same function as a fuse, but re- sets itself when current returns to normal When a fuse blows, the link in the fuse will melt and burn in half to stop the excess current Fusible Link: Small section of wire designed o burn in half when excess current is detected Circuit Breaker: Performs the same function as a fuse, but re- sets itself when current returns to normal

Relays An electronically operated switch It allows a small dash switch to control another circuit from a distant point It also allows small wires to be used behind the dash,while large wires might be needed to operate the circuit Eg.The starter circuit An electronically operated switch It allows a small dash switch to control another circuit from a distant point It also allows small wires to be used behind the dash,while large wires might be needed to operate the circuit Eg.The starter circuit

The Starting Circuit

… end of Part 2

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Using a Multi-Meter or DMM Testing for Voltage and Continuity

Testing voltage Turn on the machine and set it to ‘V’ (with dashed lines) Get a baseline reading In most automotive applications voltage will be… 12V or 24V Test the battery to get your baseline Move to your test area and perform the tests! Turn on the machine and set it to ‘V’ (with dashed lines) Get a baseline reading In most automotive applications voltage will be… 12V or 24V Test the battery to get your baseline Move to your test area and perform the tests!

Voltage Remember that voltage can only flow if there is a good path to ground. Make sure that the metal you are using for ground (black lead) is connected to the ground circuit of the vehicle Seat belt bolt, metal dash support, engine metal, etc. Remember that voltage can only flow if there is a good path to ground. Make sure that the metal you are using for ground (black lead) is connected to the ground circuit of the vehicle Seat belt bolt, metal dash support, engine metal, etc.

Continuity test THIS TEST is for fuses out of the vehicle** Set the DMM to the speaker/sound icon Then press the corresponding grey button When you touch the leads together you should hear a beep. THIS TEST is for fuses out of the vehicle** Set the DMM to the speaker/sound icon Then press the corresponding grey button When you touch the leads together you should hear a beep.

Test a fuse with continuity Set the DMM to continuity Place one probe on each test point Listen for the beep

Test a fuse IN the vehicle Set the DMM to volts Connect the black lead to ground Turn the ignition to ‘On’ (not running, but dash lights on) Test each side of the fuse. You should get 12V at each point If you don’t… You have found a blown fuse!! Set the DMM to volts Connect the black lead to ground Turn the ignition to ‘On’ (not running, but dash lights on) Test each side of the fuse. You should get 12V at each point If you don’t… You have found a blown fuse!!

Check a fuse in the vehicle Black lead to ground Ignition to ‘on’ Probe each test point Look for around 12V Black lead to ground Ignition to ‘on’ Probe each test point Look for around 12V

End of Part 3

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