# Basic Electrical Systems Theory and Repair

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Basic Electrical Systems Theory and Repair
Chapter 29 Page 387

So, Where is Electronics in a Car
Everywhere Antilock brakes, engines, emissions, dash, fuels system, transmissions, tires, suspension, windows, safety systems, lighting. ----Well, I could go on and on and on.

The Basics

Atoms Positive Negative

Conductors and Insulators

Conductors Conductors
A good conductor must not have more than four electrons in the outer valence ring of an atom. Copper is one of the best conductors; along with aluminum and gold, conductors have one electron in the outer valence ring.

Insulators Insulators
A good insulator must have more than four electrons in the outer valence ring of an atom. Rubber, glass, and porcelain are the best insulators with many electrons in the outer valence ring.

Electrical Flow

Electron Movement This is the way it really is!
Negative to Positive This is what we are taught! Positive to Negative

Wiring is coated with PVC, a flexible plastic to insulate the copper wiring.
Color Chart

Circuit Requirements = A full circle is provided
Switch 12 v Complete path Load (light) + Source (Battery) _ Source – Battery or voltage supply Load – Electrical components, lights, radio, etc. Complete path for electron flow – Wires and connections

Circuit Devices Controls Devices Protection Devices
Switches for on and off Fuses and Circuit Breakers Protect form Overloads

Fuses and Circuit Breakers

Other Symbols

Electrical Terms Voltage- Also called Electromotive Force, Pressure of electricity or the amount of force it takes to move electrons. Measured in volts. Current- The movement or flow of electrons, measured in amperes or amps for short. Resistance-Anything that impedes or slows the flow of electrons. Measured in ohms.

More Electrical Terms AC – Alternating Current (shop lights and equipment) DC – Direct Current (Auto battery and most systems) Auto voltage used is normally between 12 and 15 volts

Circuit Types Series Parallel Combination

Series Circuit

Series Circuits Series circuits provide only one path for electron flow through a circuit. When one component fails, the remaining components quit working. Light 12 v Light Light

Parallel Circuit

Parallel Circuits Parallel circuits provide two or more paths for electron flow through a circuit. When one component fails, the remaining components are not affected. 12 v Lights

Combination The simplest type is to use a switch in the first part of the circuit (series) and the rest of the circuit is wired in parallel. Lights 12 v

Ohm’s Law Greg Simon Ohm (1787 – 1854)
Ohm’s Law: It takes one volt to push one ampere of current through one ohm of resistance. *Look at page 394 for more.

E I R Ohm’s Law E = Voltage (Electromotive Force)
I = Current (Intensity) R = Resistance (Ohms) E = IR I = E/R R = E\I

E I R Ohm’s Law E = IR I = E / R R = E \ I E = IR 12 = 3 X 4 I = E / R
3 amps 12 volts I = E / R 3 = 12 / 4 R = E / I 4 = 12 / 3

Magnetism Laws of magnetism: 1. Like poles repel each other.
2. Unlike poles attract each other. 3. The attractive force increases as the distance between the magnets decreases. N S N S S N

Magnetic Fields

Magnetism Magnetic Field-
Occurs when a current is flowing through a conductor. Electromagnets- Artificially creating a magnetic field. A coil of wire with a voltage applied.

Electromagnets M Switch Battery Starter Solenoid or Relay

Electromagnets

Resistors

A Few More Terms Semiconductors- Can act as both insulator and conductor. Diode- an electronic one way check valve, it allows flow one way but doesn’t allow it to reverse the other way. Transistor- electronic relay. Its very fast, and no moving parts.

Basic Tests Meters Analog and Digital Digital Volt-ohm Meter (DVOM)
or Digital Multimeter (DMM)

Measurements

Voltage Testing

Voltage Check

Testing Voltage After Switch
Open = wire broke or fried wire

Circuit Test 3 1 = 12 v 2 = 12v 3 = 12v 1 2 2

Continuity Testing

Ohmmeter Test

Diode Check Diode is a one way street only. Reversing the multimeter leads will tell us if the voltage is allows one way and is stopped the opposite way. If it doesn’t do this toss the diode. .000 one way and 1. the other.

Testing Device with Ohmmeter with Power Removed
Continuity Should be .000 if Good Infinity Should be 1. if Bad

Testing Amps Need to change red probe lead to Amp on meter

Test Light

Test Light

Using a Jumper Wire Bypassing Ground

Bypass a Switch with Jumper Wires

Circuit Defects Open Incomplete or broken circuit. The circuits quits working. Short Two wires unintentionally connecting with each other. Could cause more than one component to operate.

Circuit Defects Ground
When a positive and negative wire contact each other. Could cause sparking and extreme heat due to high current flow. Very low resistance blows fuses, circuit breakers, or fusible links.

Circuit Defects Open Circuits

Circuit Defects Short Circuits

Circuit Defects Ground Circuits

Your Job. Complete chapter Questions 1-15 (review) and 1-10 (ASE-style). Page Write on a separate paper and write out the complete question and your answer. ( do not write the other answer options). Complete the chapter worksheet (I will give it out). You may write on it. File all items in your note book. Notebooks will be graded in the future.