Basic Electrical

Electrical Electrical BasicsBasics

“Chasing Sparks”Chasing Sparks”

What is Electricity?Everything that has substance and takes up space, whether it is solid, liquid, or gaseous, is made up of very small particles called atoms.

What is Electricity?

Scientists believe all atoms have negatively charged particles known as electrons, which revolve around a central core, or nucleus. This nucleus is believed to be positively charged, and to contain other particles known as protons and neutrons.

What is Electricity?Electrons in the inner orbit or orbits are known as bound electrons.

Those in the outer orbit are called free electrons, and can be easily forced out of their orbits, flowing from one atom to another.

Current FlowCurrent FlowThe “electron theory” states that current flow is the organized, forced movement of free electrons in a specific direction.

Continuous current flow in only one direction is known as “DC” or “Direct Current.”

Current FlowCurrent FlowFlow that alternates back and forth is called “Alternating Current.”

A good conductor is a material that has many free electrons, such as copper. Lead and gold have large numbers of free electrons.

Current FlowCurrent FlowGood conductors readily transmit electricity.

The force that causes electrons to move from one atom to another is called electromotive force (EMF).

Current FlowCurrent Flow

Electromotive force is caused by a difference in electrical potential and is measured in volts, also referred to as voltage.

Current FlowCurrent FlowWhen electrons begin to flow, the effect is felt instantly all along the surface of the conductor, very much as force can be felt all the way through a row of billiard balls.

Current FlowCurrent FlowSome older cars and heavy equipment had their positive battery terminal connected to the chassis or frame and the negative side of the circuit was switched. Practically no production vehicle uses this configuration today.

Current FlowCurrent FlowToday’s vehicles have their negative terminal battery terminal connected to the chassis or frame, also known as ground.

The positive feed The positive feed wires to vehicle wires to vehicle components all components all originate at the originate at the positive battery positive battery terminalterminal


When a switch is closed, current flows from the battery negative post to chassis ground, through the load and switch, and to the positive terminal.


Even though the ground has the excess of electrons, the positive post is the one that is generally regarded as “hot.”


“Electron theoryElectron theory” supposes current flow to be from negative to positive, while “Conventional Theory” supposes the current flows from positive to negative.


Thus, the current in automotive circuits is usually traced from the source (battery) to the load (bulb, motor, etc.) and then to ground.

Sources of ElectricitySources of Electricity

A battery is a chemical source of electricity. It contains a number of positive plates and an equal number of negative plates.


The positive The positive and negative and negative plates are plates are immersed in an immersed in an electrolyte electrolyte solution solution composed of composed of water and water and sulphuricsulphuric acid.acid.


When the battery is When the battery is charged, a charged, a chemical reaction chemical reaction of the acid on the of the acid on the plates results in an plates results in an excess of electrons excess of electrons collecting on the collecting on the negative plates.negative plates.


If a conductor is If a conductor is connected connected between the between the plates, current plates, current (electrons) will flow (electrons) will flow through the through the conductor from conductor from one plate to the one plate to the other.other.

Electromagnetic Electromagnetic InductionInduction

When a When a conductor conductor connected to a connected to a closed circuit is closed circuit is passed through a passed through a magnetic field, magnetic field, current is current is produced in the produced in the conductor.conductor.

Electromagnetic Electromagnetic InductionInduction

Alternators, generators, and Alternators, generators, and various inductive sensors various inductive sensors use this principle to do their use this principle to do their work.work.

Static ElectricityStatic ElectricityElectrons can Electrons can move from one move from one body of matter to body of matter to another by another by friction. Scuffing friction. Scuffing your shoes on your shoes on carpet on a cold, carpet on a cold, dry day can dry day can cause a nice zap! cause a nice zap!

LightningLightning is is another form another form of of static static electricityelectricitydischarging discharging from the from the atmosphere atmosphere to the earth.to the earth.

Electrical CircuitsElectrical Circuits

Electrical CircuitsElectrical Circuits

An electrical circuit is a complete path for current flow… basically defined as being froma power source to a load component that has resistance and uses electricity to do its work, and finally a ground path back to the negative terminal of the power source.

Circuit ComponentsCircuit Components

One component necessary for all circuits is a power source.

In an automobile, the power source is the battery when the engine is switched off and the alternator when the engine is running..


Conductors are wires and cables, usually protected from each other and ground by insulation, and they carry the current in an electrical circuit.


Note: In an automotive circuit, the vehicle

chassis and the engine block are actually conductors in the

circuit.


Controls (switches) are necessary to turn the circuit on and off.

Circuit ComponentsCircuit ComponentsThe Load is a device that uses up electricity and turns it into work.

Light bulbs and motors are among the examples of loads in an automotive circuit


The Circuit Protector is a device that protects the conductors and components in a circuit in case of an overload.

Current Will Flow Current Will Flow IF...IF...

• The switch is closed

• The circuit protector is not open

• Charge is available

Ohm’s LawOhm’s Law

Ohm’s Law is the basic rule for the relationships between voltage, current, and resistance.

1. CURRENT FLOW IS DIRECTLY PROPORTIONAL TO VOLTAGE

2. CURRENT FLOW IS INVERSELY PROPORTIONAL TO RESISTANCE

Ohm’s LawOhm’s Law1. CURRENT FLOW IS DIRECTLY PROPORTIONAL TO VOLTAGE:

Simply put, this means that an increase in VOLTAGE will cause an INCREASE in current flow. This is true because voltage is, in effect, electrical “pressure.” The higher the voltage, the higher the pressure, thus the higher the current flow. Remember:

1 volt pushes 1 amp through 1 ohm.


2. CURRENT FLOW IS INVERSELY PROPORTIONAL TO RESISTANCE

This statement means that an increase in RESISTANCE will cause a DECREASE in current flow.

Ohm’s LawOhm’s LawHigh current flow…

Added resistance…

Lower Current flow


Voltage Voltage equalsequalsCurrent Current timestimesResistance

“E” is used to denote volts.

“R” denotes resistance.

“I” denotes current.

Resistance

Ohm’s LawOhm’s Law1 volt pushes 1 amp

through 1 ohm, right? Okay, how many amps will 12 volts push through 6

ohms?

Resistance — 2 ohms

Draw — 5 AmpsResistance — 2 ohms

Draw — 6 Amps

10 volts

12 volts

Voltage is Voltage is like like

PressurePressure

Voltage is like PressureVoltage is like PressureNOTE:

Increasing voltage in a given circuit always increases current draw.

Voltage is like PressureVoltage is like PressureVoltage is also Voltage is also expressed as a expressed as a “difference in “difference in potential” when it potential” when it refers to refers to electromotive electromotive force caused by a force caused by a difference in difference in electrical charges electrical charges between two between two points in a circuit.points in a circuit.

CurrentCurrent

Current is Current is the flow of the flow of electrons electrons between two between two points in a points in a closed closed circuit that circuit that have a have a difference in difference in potential.potential.

CurrentCurrent

The unit of The unit of measurement measurement to determine to determine current flow is current flow is the the ampere ampere (abbreviated (abbreviated “amp”).“amp”).

CurrentCurrent

One ampere is One ampere is defined as the defined as the movement of movement of one one coulombcoulombof electrons of electrons past a given past a given point in one point in one second. Asecond. Acoulomb is coulomb is one billion one billion billion billion electrons.electrons.

CurrentCurrent

Current is Current is thus a thus a measure of measure of the rate of the rate of electrical flow. electrical flow.

It can also be It can also be known as known as amperageamperage or or drawdraw, , and is and is measured with measured with anan ammeterammeter..

CurrentCurrent

When two When two loads are loads are connected connected parallel, as in parallel, as in the illustration the illustration on the left, on the left, each draws each draws current current independently independently of the other.of the other.

CurrentCurrent

In the picture, In the picture, bulb A draws bulb A draws 2 amps, while 2 amps, while bulb B draws bulb B draws 1 amp. The 1 amp. The total current total current flow in the flow in the circuit is 3 circuit is 3 amps.amps.

CurrentCurrent

In the picture, In the picture, bulb A draws bulb A draws 2 amps, while 2 amps, while bulb B draws bulb B draws 1 amp. The 1 amp. The total current total current flow in the flow in the circuit is 3 circuit is 3 amps.amps.

CurrentCurrent

Important:Important:

The total The total current draw current draw in a parallel in a parallel circuit equals circuit equals the sum of the the sum of the individual individual current draws.current draws.

CurrentCurrent

If the same two If the same two bulbs are bulbs are connected in connected in series instead of series instead of parallel, their parallel, their combined combined resistance will resistance will bebe 18 ohms18 ohms..

CurrentCurrent

0.67 amps X 18 ohms = 12 v

12 v/ 18 ohms = 0.67 amps

ResistanceResistance


Resistance is an opposition to current flow offered by a load or a resistor.


Even conductors have some Even conductors have some resistance; for example, a resistance; for example, a piece of 22 gauge copper wire piece of 22 gauge copper wire 60 feet long has one ohm of 60 feet long has one ohm of resistance. Larger diameter resistance. Larger diameter wires have less resistance.wires have less resistance.


HeatHeat generally causes generally causes resistance to increase in a resistance to increase in a conductor or connection.conductor or connection.

ResistanceResistanceAn interesting and somewhat volatile An interesting and somewhat volatile relationship exists between heat and relationship exists between heat and resistance in electrical wiring…resistance in electrical wiring…

ResistanceResistanceSince every connection has some Since every connection has some resistance, that resistance produces resistance, that resistance produces heat…heat…

ResistanceResistance……and that heat producesand that heat produces more more resistanceresistance, , which in turn produceswhich in turn produces more more heatheat until current finally stops flowing and until current finally stops flowing and the component fails.the component fails.


When resistors are in When resistors are in seriesseries, the total , the total resistance is the sum of the individual resistance is the sum of the individual resistances… 6+6 = 12resistances… 6+6 = 12


When resistors are in When resistors are in parallelparallel, the total , the total resistance equals the source voltage resistance equals the source voltage divided by the combined current draw.divided by the combined current draw.


With a 12 volt supply, how much With a 12 volt supply, how much amperage would amperage would eacheach of these of these

resistors pull?resistors pull?



So each 6 ohm resistor will pull 2 amps.

And 2 + 2 = 4


Okay, if the total circuit pulls Okay, if the total circuit pulls 4 amps4 amps, how , how many many ohmsohms of resistance would the total of resistance would the total circuit have, based on a 12 volt supply?circuit have, based on a 12 volt supply?





Let’s try a different combination. With a 12 Let’s try a different combination. With a 12 volt source, how much total resistance volt source, how much total resistance

would this parallel circuit have?would this parallel circuit have?


_______________Amps_______________Amps

+_______________Amps+_______________Amps

Equals __________Amps total.Equals __________Amps total.




Voltage DropIt’s a basic rule for closed circuits that the voltage “used up” or “dropped” in the loads must be equal to the source voltage.

Voltage DropThe voltmeter at point A will measure the source voltage.

If the voltage measurement is taken at point B, what will the voltage be?

Voltage DropDid you say zero volts? You’d be right.

The voltage drop is equal to 12 times zero, which comes to zero volts.

Voltage DropWhen two or more loads are in series:

1. The voltage drop of each load is equal to current draw times resistance.

(E = I X R)

Voltage Drop

2. The sum of all voltage drops equals the source voltage.

Voltage Drop

That is, the closer you move your probe to the ground side of a circuit...

Voltage Drop

…the lower the measured voltage will be.

Voltage Drop

Thus in the example shown here:

Total Resistance = 6

ohms, and draw = 2 amps.

Voltage Drop

The voltage drop at the brightness control is 2

amps x 3 ohms, which equals 6

volts.

Voltage Drop

Thus available

voltage to the bulb is only 6

volts

Computing Parallel Resistances by Formula


If all the resistances are

equal, divide the resistance

of one alone by the number of

resistors.


In this example,

12/4 = 3 ohms resistance.


If there are only two resistances,

multiply their values and

divide by the sum of their

values.


In this example:


For any three or more resistances,

first find their “reciprocals,” then add the reciprocals

together and divide the total by

one.


In this example:

Power Sources and Grounds

Power SourcesThe storage

batteryprovides

current to all electrical systems

when the key is on and the engine is off.

Power SourcesThe generator maintains the charge in the battery after the engine is started and supplies electrical

current to all electrically powered equipment.

Grounds

Case Grounds are used where the

component itself is securely attached to a well-grounded part of the vehicle.

Grounds

Remote Grounds are used where

the component itself is not grounded...

Grounds

...or where the remote ground is used to control the component. Examples are reversible motors (power windows, door locks) and instrument panel warning indicator lamps.

Reading Schematics

Basic Rule: The top of most schematics is usually “hot” and the bottom is usually “ground”.

Let’s start by tracing power from hot to ground...

Power is fed to the fuse...

Through circuit 295and connector C172.. The male side of the connector is C172M, while the femaile side is C172F.

Okay, let’s stop right here. Where is Connector C172? How do you find it?

Most wiring books have a location view like this.

Using the numbers and letters, find C172 at A 6

Notice that C172F is on the left and C172M is on the right… These are mating connectors.

Find circuit 295. What is the pin number? What color is the wire? Write down both pieces of information.

Locate the wire where it passes through a connector

Now we not only know where C172 is...

…we also know what the connector pinout looks like, AND...

…we know which pin is number 34 on the connector

There are three things we should notice about this current path.

#1: The truck could have either of two switches, depending on whether it is equipped with a manual or automatic transmission. This is drawn as an “alternate current path.”

#2: the wires going into and out ofthe switch in question bothpass through connector C172.

#3: After the circuit passes through the switch, the circuit number changes from 295 to 140.

Find circuit number 140. What is the pin number? Write it down.

With that in mind, we inspect all four pins, i.e., the MALE and FEMALE pins 34 and 32. Finding no problem, we move on...

We know now that pins 34 and 32 are both part of the backup lamp circuit and that either pin could be the cause of a problem.

Now the circuit passes through a splice and two more connectors. The splice could be a problem, but it is usually taped into the harness and can be difficult to locate. It should be examined last.

Let’s find connector C148 in our location drawing:

Find D10 on the grid and locate connector C148.

This pinout legend is slightly different. Find circuit 140 and double check the wire color to make sure we’re still on track… Write down the pin number.

Once again, we can find the connector on the vehicle, then locate the pin in that connector so that we can check the integrity of the circuit at the connector.

Now let’s go on to find C411 the same way...

Find F7 on the grid and locate connector C411.

The circuit number we’re looking for is still 140. Find it and write down the pin number. Once again, we can go to this connector, find the pin in question, and check the circuit.

Our last inline connector is C 403. Let’s find it on the vehicle like we did the others.

Find E10 on the grid and locate connector C403.

The circuit number we’re looking for is still 140. Find it and write down the pin number. Once again, we can go to this connector, find the pin in question, and check the circuit. By this time we should have a pretty good idea where the problem is, if we haven’t already found it.

One more potential problem point is the ground, namely G104. Let’s locate it.

Find E10 on the grid and locate connector G104.

…but on the schematic the

ground looks very close to the lamps.

Distance is not indicated on a schematic…

Notice that the ground for the

backup lamps is at the opposite end

of the vehicle from the lamps…

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Basic Electrical