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ELECTRICAL FUNDAMENTALS
ELECTRICAL CHARGES
Opposite electrical charges always attract each other. So these particles with
opposite charges will tend to move toward each other. Like electrical charges
always repel. So particles with like charges will move away from each other.
Remember: Opposites charges attract, and like charges repel.
Atoms always try to remain electrically balanced.

INSULATORS
An INSULATOR is any material that inhibits (stops) the flow of
electrons (electricity).
An insulator is any material with 5 to 8 free electrons in the outer
ring.Because, atoms with 5 to 8 electrons in the outer ring are
held (bound) tightly to the atom, they CANNOT be easily moved
to another atom nor make room for more electrons.
Insulator material includes glass, rubber, and plastic.

CONDUCTORS
A CONDUCTOR is any material that easily allows
electrons (electricity) to flow.A CONDUCTOR has 1 to 3
free electrons in the outer ring.Because atoms with 1 to
3 electrons in the outer ring are held (bound) loosely to
the atom, they can easily move to another atom or
make room for more electrons.Conductor material
includes copper and gold.

SEMICONDUCTORS
Any material with exactly 4 free flectrons in the outer
orbit are called SEMICONDUCTORS.
A semiconductor is neither a conductor or insulator.
semiconductor material includes carbon, silicon, and
germanium.
These materials are be used in the manufacturer of
diodes, transistors, and integrated circuit chips.

Two Current Flow theories exist.
The first is: ELECTRON THEORY
The Electron Theory states that current flows
from NEGATIVE to POSITIVE. Electrons move
from atom to atom as they move through the
conductor towards positive.

The second Current Flow theory is:
CONVENTIONAL THEORY
Conventional theory, also known as HOLE THEORY,
states that current flows from POSITIVE to
NEGATIVE. Protons or the lack of electrons (the
holes) move towards the negative. (Current flow
direction in Hole Theory is the opposite of that in
Electron Theory.)

VOLTAGE
Voltage is the electrical force that moves electrons through a conductor.
Voltage is electrical pressure also known as EMF (Electro Motive Force)
that pushes electrons.
The greater the difference in electrical potential push (difference
between positive and negative), the greater the voltage force potential.

MEASUREMENT
A VOLTMETER measures the voltage
potential across or parallel to the circuit.
The Voltmeter measures the amount of
electrical pressure difference between
two points being measured.Voltage can
exist between two points without electron
flow.

VOLTAGE UNITS
Voltage is measured in units called VOLTS.
Voltage measurements can use different value prefixes such as
millivolt, volt, Kilovolt, and Megavolt.

CURRENT (AMPERES)
CURRENT is the quantity or flow rate of
electrons moving past a point within one
second. Current flow is also known as
amperage, or amps for short.
Higher voltage will produce higher current
flow, and lower voltage will produce lower
current flow.

MEASUREMENT
An AMMETER measures the quantity of current flow. Ammeters are placed in
series (inline) to count the electrons passing through it.
Example: A water meter counts the gallons of water flowing through it.

AMPERAGE UNITS
Current flow is measured in units called Amperes or AMPS.
Amperage measurements can use different value prefixes, such as
microamp, milliamp, and Amp.

AFFECTS OF CURRENT FLOW
Two common effects of current flow are Heat Generation and
Electromagnetism.
HEAT: When current flows, heat will be generated. The higher the current flow
the greater the heat generated. An example would be a light bulb. If enough
current flows across the filament, it will glow white hot and illuminate to produce
light.
ELECTROMAGNETISM: When current flows, a small magnetic field is created.
The higher the current flow, the stronger the magnetic field. An example:
Electromagnetism principles are used in alternators, ignition systems, and other
electronic devices.
RESISTANCE
Resistance is the force that reduces or stops
the flow of electrons. It opposes voltage.
Higher resistance will decrease the flow of
electrons and lower resistance will allow more
electrons to flow.

MEASUREMENT
An OHMMETER measures the resistance of an
electrical circuit or component. No voltage can be
applied while the ohmmeter is connected, or
damage to the meter will occur.
Example: Water flows through a garden hose, and
someone steps on the hose. The greater the
pressure placed on the hose, the greater the hose
restriction and the less water flows.
RESISTANCE UNITS
Resistance is measured
in units called OHMS.
Resistance
measurements can use
different value prefixes,
such as Kilo ohm and
Megaohms.

RESISTANCE FACTORS
Various factors can affect the resistance. These include:
LENGTH of the conductor. The longer the conductor, the higher the
resistance.
DIAMETER of the conductor. The narrower the conductor, the higher the
resistance.
TEMPERATURE of the material. Depending on the material, most will
increase resistance as temperature increases.
PHYSICAL CONDITION (DAMAGE) to the material. Any damage will
increase resistance.
TYPE of MATERIAL used. Various materials have a wide range of
resistances.
TYPES OF ELECTRICITY
Two basic types of Electricity classifications:
STATIC ELECTRICITY is electricity that is standing still. Voltage potential with
NO electron flow.
DYNAMIC ELECTRICITY is electricity that is in motion. Voltage potential
WITH electron flow. Two types of Dynamic electricity exist:
Direct Current (DC) Electron Flow is in only one direction.
Alternating Current (AC) Electron flow alternates and flows in both directions
(back and forth).

STATIC ELECTRICITY
Voltage potential with NO electron flow.
Example: By rubbing a silk cloth on a glass
rod, you physically remove electrons from
the glass rod and place them on the cloth.
The cloth now has a surplus of electrons
(negatively charged), and the rod now has a
deficiency of electrons (positively charged).
Another example: Rub your shoes on a rug
and then touch a metal table or chair ....
Zap!! The shock you felt was the static
electricity dissipating through your body.
DYNAMIC ELECTRICITY
is electricity in motion, meaning you
have electrons flowing, in other words
voltage potential WITH electron flow.
Two types of dynamic electricity exists:
Direct Current (DC)
Alternating Current (AC)

DIRECT CURRENT (DC)
Electricity with electrons flowing in only one direction is called Direct Current or DC.
DC electrical systems are used in cars.

ALTERNATING CURRENT (AC)
Electricity with electrons flowing back
and forth, negative - positivenegative, is called Alternating
Current, or AC.
The electrical appliances in your
home use AC power.

SOURCES OF ELECTRICITY
Electricity can be created by several means: Friction, Heat, Light,
Pressure, Chemical Action, or Magnetic Action.
Only a few of these sources of energy are used in the automobile. The
battery produces electricity through chemical action, and the alternator
produces electricity through magnetic action.
Friction creates static electricity.
Heat can act upon a device called a thermo couple to create DC.
Light applied to photoelectric materials will produce DC electricity.
Pressure applied to a piezoelectric material will produce DC electricity.
Chemical Action of certain chemicals will create electricity.

ELECTRICAL CIRCUITS
AN ELECTRICAL CIRCUIT
The circuit shown below has a power source, fuse, switch, two lamps and
wires connecting each into a loop or circle. When the connection is complete,
current flows from the positive terminal of the battery through the wire, the
fuse, the switch, another wire, the lamps, a wire and to the negative terminal
of the battery. The route along which the electricity flows is called an electrical
circuit.
ELECTRICAL CIRCUIT REQUIREMENTS
A complete Electrical Circuit is required in order to
make electricity practical. Electrons must flow from and
return to the power source.
There are three different circuit types, all require the
same basic components:
1. Power Source is needed to supply the flow of
electrons (electricity).
2. Protection Device prevents damage to the circuit in
the event of a short.
3. Load Device converts the electricity into work.
4. Control Device allows the user control to turn the
circuit on or off
5. Conductors provide an electrical path to and from the
power source.

BASIC CIRCUIT CONSTRUCTION
1. Power Source (Battery, Alternator,
Generator, etc.)
2. Protection Device (Fuse, Fusible Link,
or Circuit Breaker)
3. Load Device (Lamp, Motor, Winding,
Resistor, etc.
4. Control (Switch, Relay, or Transistor)
5. Conductors (A Return Path, Wiring to
Ground)

LOADS
The illustration below has a horn in
place of the lamp. Any device such
as a lamp, horn, wiper motor, or rear
window defogger, that consumes
electricity is called a load. In an
electrical circuit, all loads are
regarded as resistance. Loads use
up voltage and control the amount of
current flowing in a circuit. Loads
with high resistance cause less
current to flow while those with lower
resistance allow high current rates
to flow.

AUTOMOTIVE ELECTRICAL CIRCUITS
In an automotive electrical circuit, one end of the wire from each load
returning to the battery is connected to the vehicle body or frame.
Therefore, the vehicle body or frame itself functions as a conductor,
allowing current to flow though the body or frame and back to the
battery. The body or frame is then referred to as the body ground (or
earth) of the circuit (meaning that part of the circuit that returns the
current to the battery).

WHAT IS OHM'S LAW?
A simple relationship exists between voltage, current, and resistance in electrical circuits.
Understanding this relationship is important for fast, accurate electrical problem diagnosis and
repair.
OHM'S LAW
Ohm's Law says: The current in a circuit is directly proportional to the applied voltage and
inversely proportional to the amount of resistance. This means that if the voltage goes up, the
current flow will go up, and vice versa. Also, as the resistance goes up, the current goes down,
and vice versa. Ohm's Law can be put to good use in electrical troubleshooting. But calculating
precise values for voltage, current, and resistance is not always practical ... nor, really needed.
A more practical, less time-consuming use of Ohm's Law would be to simply apply the concepts
involved:
SOURCE VOLTAGE is not affected by either current or resistance. It is either too low, normal,
or too high. If it is too low, current will be low. If it is normal, current will be high if resistance is
low, or current will be low if resistance is high. If voltage is too high, current will be high.
CURRENT is affected by either voltage or resistance. If the voltage is high or the resistance is
low, current will be high. If the voltage is low or the resistance is high, current will be low.
RESISTANCE is not affected by either voltage or current. It is either too low, okay, or too high. If
resistance is too low, current will be high at any voltage. If resistance is too high, current will be
low if voltage is okay.
NOTE: When the voltage stays the same, such as in an Automotive Circuit... current goes up
as resistance goes down, and current goes down as resistance goes up. Bypassed devices
reduce resistance, causing high current. Loose connections increase resistance, causing low
current.

TYPES OF CIRCUITS
Individual electrical circuits normally combine one or more resistance or load
devices. The design of the automotive electrical circuit will determine which type
of circuit is used. There are three basic types of circuits:
Series Circuit
Parallel Circuit
Series-Parallel Circuit
SERIES CIRCUITS
A series circuit is the simplest circuit. The
conductors, control and protection
devices, loads, and power source are
connected with only one path to ground
for current flow. The resistance of each
device can be different. The same
amount of current will flow through each.
The voltage across each will be different.
If the path is broken, no current flows
and no part of the circuit works.
Christmas tree lights are a good
example; when one light goes out the
entire string stops working.

VOLTAGE DROP
A voltage drop is the amount of
voltage or electrical pressure that is
used or given up as electrons pass
through a resistance (load). All
voltage will be used up in the circuit.
The sum of the voltage drops will
equal source voltage. A voltage drop
measurement is done by measuring
the voltage before entering the load
and the voltage as it leaves the load.
The difference between these two
voltage readings is the voltage drop.

PARALLEL CIRCUIT
A parallel circuit has more than one
path for current flow. The same
voltage is applied across each branch.
If the load resistance in each branch is
the same, the current in each branch
will be the same. If the load resistance
in each branch is different, the current
in each branch will be different. If one
branch is broken, current will continue
flowing to the other branches.

SERIES PARALLEL CIRCUIT
A series-parallel circuit has some components in series and others in
parallel. The power source and control or protection devices are usually in
series; the loads are usually in parallel. The same current flows in the series
portion, different currents in the parallel portion. The same voltage is
applied to parallel devices, different voltages to series devices. If the series
portion is broken, current stops flowing in the entire circuit. If a parallel
branch is broken, current continues flowing in the series portion and the
remaining branches.

Wiring Harness

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