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INTRODUCTION TO

ELECTRICAL THEORY

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What is Electricity?

• The controlled flow of electrons in an electrical circuit.

• A circuit must always be a complete loop.

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Building Blocks

• Atoms

• Nucleus

• Protons (+)

• Neutrons

• Electrons (-)

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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

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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

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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