1 INTRODUCTION TO ELECTRICAL THEORY 2 What is Electricity? The controlled flow of electrons in an...
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Transcript of 1 INTRODUCTION TO ELECTRICAL THEORY 2 What is Electricity? The controlled flow of electrons in an...
1
INTRODUCTION TO
ELECTRICAL THEORY
2
What is Electricity?
• The controlled flow of electrons in an electrical circuit.
• A circuit must always be a complete loop.
3
Building Blocks
• Atoms
• Nucleus
• Protons (+)
• Neutrons
• Electrons (-)
4
Watch polarity
• Don’t cross wires
• +
• -
• Polarity plugs
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ATOMS
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Conductors• Let electricity flow readily• Few electrons in outer shell
• 1 or 2 electrons
• Free electrons in outer shell• Copper, gold, silver• Platinum, aluminum, water
2S
8p
7
Insulators
• Do not let electrons flow
• Outer shell full or close to full• 6-7-8 electrons
• Full outer electron shell• Glass, plastic
• Porcelain, wood
• Rubber
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Circuit Essentials
• Source – Battery and Alternator• Path – Wires or Chassis
• Wire size determine amp flow• Wire measure in gauge (AWG)• Bigger gauge = smaller wire
• Load – The device the electricity runs: motors, lamps, sensors, relays or electronic devices.
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Other Circuit Components• Switches• Circuit Protection
• Fuse• Circuit breaker• Voltage limiter• Fusible link
• Resistors• Fixed• Variable
• Relays• Allows small current to
control a large current• ie Computer controls motor
• Solenoids• Capacitors• Integrated Circuits• Wiring• Printed Circuit Boards• Wiring Diagrams
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TYPES of CIRCUITS
• Simple• Chassis ground
• One wire
• Series
• Parallel
• Series/parallel
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SIMPLE CIRCUIT/1 wire
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SERIES CIRCUIT
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PARALLEL CIRCUIT
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SERIES / PARALELL
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Electrical terms
• Circuits• Open
• Closed
• Continuity
• Shorts• Open (wire broken)
• Short circuit (2 hot wires touch)
• Short to ground (wire to chassis)
• current increases
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Shorts• Shorts
• Open (wire broken)
• Short circuit (2 hot wires touch)
• Short to ground (wire to chassis)
• current increases
17
Three Measures of Electricity
• Voltage or Volts. This the push on the electrons by the source. In fancy terms known as electromotive force.
• Amperes or Amps. This measure is literally the amount of electrons. A coulomb is 6 billion billion electrons.
• Resistance. The resistance or opposition to the flow of electrons usually in the load device. Measured in Ohms.
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OHM’s Law
• E = Voltage
• I = Current
• R = Resistance
• ---------------------------
• It requires one VOLT to push one AMP through one OHM of resistance.
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E = VOLTAGE
• E = I x R
• 2 amps
• x
• 5 ohms
• =
• 10 volts
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VOLTAGE
• The push of the electricity
• Labeled E or V• Magnetic
• Chemical
• Measured in Volts
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CURRENT
• The Amount of Electricity
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Current
• Direct current• Cars
• Batteries
• AC - households• Alternating current
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I = Current
• I = E / R
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Resistance
• Opposition to the flow of Electrons
• Measured in OHMs
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R = Resistance
• R = E / I• IF R = 0
• THERE IS RESISTANCE…• Just very very low
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Resistance is affected by . . .
• Diameter of the wire
• Temperature of the wire
• Length of the wire
• Material wire if made from
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Resistance Total
• Series circuit• Rt = R1+ R2 + R3 + . . .
• Parallel 2 resistors• (R1xR2) / (R1+R2)
• Parallel with More than 2 resistors• (1)
• (1/R1) + (1/R2) + (1/R3) + (1/r4) + (1/Rx)
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Electron Theory
• Electricity moves from - to +
• Electricians
• Scientists
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Conventional Theory
• Electricity moves from + to –
• Automotive
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MEASUREMENT TOOLS
• Voltage Meter
• Multi-Meter
• Test Light
• DVOM
• AMMETER
• Scan Tools
• Scope
• Jumper wires
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Meter Hook-Ups
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Electromagnetism • Fundamentals of Magnetism
• Like charges repel• Dissimilar charges ATTRACT
• Magnetic fields surround a wire• flux
• Magnetic Circuits and Resistance• Starters• Solenoids• alternators
• Induced Voltage• Magnets can form voltage• Voltage can form magnets• Wire passes a magnet forces electrons to move in the wire------; current
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Meter hook up
• Measure voltage in parallel hook up
• Measure amperage in series
• Measure resistance with the circuit off
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PREFIXES
• Milli = .001
• BASE
• Kilo = 1000
• Mega = 1000000
• Thus 1 mV = .001V = .000001KV = .000000001 MV
• OR
• 1MV = 1000KV = 1000000V = 1000000000mV