KIA TRAINING BASIC ELECTRICITY

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Basic Electricity

Published by Chonan Technical Service Training Center

INTRODUCTION

Today’s automobiles are becoming even more dependent on electrical and electronic technology to

manage systems that control power train, passenger compartment, and safety devices Because of

this, it is very important that automotive technicians have a good understanding of how electricity

works, both in theory and practical application

KIA Motors Technical Service Training Department is aware of the daily challenge technicians face

when diagnosing a vehicle with electrical or electronic problems We also understand the specialized

knowledge required to effectively isolate, troubleshoot and repair electrical problems which may occur

in a vehicle

In consideration of this, we have developed this new course titled, “Basic Electrical Training” as

part of our training program This course is designed to be instructed in two segments; first a

“refresher” reviewing basic electrical principles (such as circuit types, Ohm’s Law, and schematic

diagram reading); and second (and most important), learning how to apply the theory to diagnose

actual on-vehicle circuitry

Through carefully prepared worksheets, students will learn how to pinpoint circuit locations, conduct

measurements, and determine how voltage, current or resistance values contribute toward determining the necessary repair

This course has been design to be instructed mainly in a workshop environment with the intent of

demonstrating the practical “on-vehicle” application of the course content It is our hope that use of

this training technique will optimize the individual learning experience and technicians will relate the

knowledge gained directly to vehicle repairs at the dealership

We at KIA motors hope that the information received during this course improves technician’s

knowledge of electricity and electronics We also encourage that the procedures shown become part

of each technician’s regular diagnostic routine and are applied whenever possible to help ensure

customers receive the best possible service

Contents

1 Electricity General ··· 2 8 Magnetic Force ··· 65

1.1 Fundamental ··· 2 8.1 Occurrence of Magnetic Force ··· 65

1.2 Occurrence of Electricity ··· 3 8.2 Magnetic and Magnetic Force ··· 65

2 Current, Voltage & Resistance ··· 13 8.3 Electro Magnetic Induction ··· 68

2.1 Current ··· 13 8.4 Solenoid ··· 69

2.2 Potential difference VS Current ··· 14 8.5 Electromagnets ··· 70

2.3 Voltage ··· 16 8.6 Relay ··· 71

2.4 Potential difference VS Voltage ··· 16 8.7 Transformers ··· 73

2.5 Resistance ··· 19 9 Capacitor ··· 81

2.6 Conductor, Insulator and resistor ··· 20 9.1 Capacitance and the Capacitor ··· 81

2.7 Current, Voltage and Resistance Relation ··· 21 9.2 Calculating Capacitor ··· 83

2.8 Direct & Parallel Current Circuit ··· 25 9.3 Types of Capacitor ··· 84

3 Ohm’s Law ··· 33 9.4 Transient Response of Capacitor ··· 86

3.1 Determining Current ··· 34 9.5 RC Time Constant ··· 88

3.2 Determining Resistance ··· 35 9.6 Capacitors in Series and Parallel ··· 89

3.3 Determining Voltage ··· 36 10 Generator ··· 91

3.4 Voltage drop ··· 36 10.1 Magnetic Induction ··· 91

4 Kirchoff’s Law ··· 39 10.2 Construction of a Generation ··· 94

4.1 Kirchoff’s Current Law ··· 39 10.3 Types of Generator ··· 97

4.2 Kirchoff’s Voltage Law ··· 40 10.4 Voltage and Current Regulation ··· 101

5 Electric Power and Watt ··· 43 10.5 Alternating Current ··· 102

5.1 Electric Power ··· 43 10.6 The Alternator ··· 104

5.2 A mount of Electric Power ··· 43 11 DC Motor ··· 107

6 Summery for basic Electrical ··· 45 11.1 Motor Operation Principles ··· 107

6.1 To understand easily formula of electrical ·· 45 11.2 Counter Electromotive Force ··· 110

6.2 Troubleshooting methods in Circuit ··· 46 11.3 DC Motors ··· 111

6.3 Check for Ground condition in Parallel circuit ··· 46 11.4 Types of Motors ··· 113

7 Multi Meter ··· 51 11.5 Start Motor ··· 114

7.1 Measurement Items (Analog Multi Meter) ··· 51 Appendix ··· 117

7.2 Volt meter ··· 54

7.3 Ohm Meter ··· 56

7.4 Digital Meter ··· 59

1 Electricity General

1.1 Fundamental

Everything in the universe is made up of matter

Matter can be defined as anything that occupies space or has mass

Matter can be found in the form of solids, liquids, and gases However, these states are subject to

relative temperature Water is usually found in liquid form Yet water can be readily changed to solid or

a vapor form by changing its temperature Matter can also be described by color, taste, and aridness,

but these are only observable characteristics They may not truly identify a substance

To truly identify a substance, the substance must be broken down into its smallest parts The

substance must be described in term of its atomic structure Only then can it truly be defined and it’s

behavioral characteristic identified

A substance has been broken down to its purest form when breaking it down further it down further

will change its atomic characteristics This form is called an element There are over 100 elements

Most of these elements occur naturally in our universe Some of the elements do not occur naturally,

but have been created in laboratories Some common examples of naturally occurring elements are

iron, copper, gold, aluminum, carbon, and oxygen

If two or more of these elements are mixed together, a compound is created A compound can be

reduced to its individual elements

An element can be reduced to its atomic structure

Substance Element Atom

Figure 1-1

1.2 Occurrence of electricity

1.2.1 what is electricity?

First, need to understand about structure of material before understand electricity

Structure of material is composed as following

Material Molecule Atom

Figure 1-2 Structure of material

Characteristic of molecule and atom

Melecul : Atom has propensity of material being minimum unit that can no longer split

Atom : It is material that can no longer split no nature of material

Atom makes of following element again, and the structure is with figure

Structure of Atom Detail structure of Atom

Figure 1-3 Structure of Atom

Protons located in the nucleus of an atom, are the positive (+) charged particles

Neutrons also in the nucleus, have no electric charge and are electrically neutral

Electrons are the particles that orbit the nucleus and have a negative (-) charge

Proton Electron

Electrons move or flow from atom to atom because it is possible for an atom to gain or lose electrons

in certain circumstances

Electrons that have been driven from an atom are called free electrons

The loss of one electron means the atom has an extra proton, which results in a more positive charge

than negative Positively charged atoms attract free electrons to replace the ones that were lost

If an atom gains an extra electron, it will have a more negative charge The atom will repel other

Negatively charged particles and will easily give up this extra electron if it is attracted away by a

positively charged atom

To understand this better, think of a line of cars in traffic on a highway When one car turns off, an

opening is available When an opening is available, another car, wanting in, sees it and is attracted to

it and fills it in

This movement or flow of free electrons from one atom to another is electrical current or electricity

1.2.2 Ionization

The number of electrons and protons that make a particular atom are usually equal in number

This equal number creates a canceling effect between the negative and positive charge

The atomic structure of each element can be described as having a fixed number of electrons in orbit

Usually, an atom remains in its normal state unless

energy is added by some exterior force such as

heat, friction, or bombardment by other electrons

When energy is added to an atom, the atom

becomes excited If the exterior force is

of sufficient strength, electrons

in the atoms outer rings or

orbits can leave their orbit

How tightly bound these outer

electrons are to an atom depends

on the element and the number

of electrons in the outer orbit

If electrons leave the outer orbit,

the atom becomes out of balance electrically

Figure 1.4 Atom ionization

When the electron leaves the outer orbit The atom becomes ionized An atom that loses an electron

from its outer orbit has more protons The atom becomes a positive ion and displays positive

charged characteristics

When an atom gains an extra electron, it becomes a negative ion Negative ions display negatively

charged characteristics

1.2.3 Electrostatic Field

The field or force surrounding a charged body is called the electrostatic field or dielectric field The

field can exhibit a positive or negative charge depending on a gain or loss of electrons Two charged

masses are shown in Figure 1-6 Lines represent the electrostatic fields of opposite polarity and the

attractive force existing between the masses In Figure 1-7, two charged masses are shown with like

polarities A repulsive force exists the charged masses due to the electrostatic fields The field

strongest very close to charged body The field strength diminishes at a distance inversely

proportional to the square of the distance

When two electrostatic fields are joined together, the electrons flow from the mass with an excess of

electrons to the mass that has a need of electrons flow from the mass with excess of electrons

Figure 1-8 illustrates this principle The excess electrons flow from the body that is negatively

charged to the positively charged body that has electron deficiency This transfer of electrons can be

accomplished by touching the two bodies together or by connecting them with a material that supports

the flow of electrons between the two bodies This connecting material is known as a conductor

because it conducts electricity

Figure 1-8 When two charged bodies are connected with a conductor,

Excess electrons will flow through the conductor from he mass having a surplus of

electrons to the mass having a deficit of electrons

1.2.4 Electron Movement

The actual flow of current through the circuit is based on the principles you have just learned As you

saw earlier, normal atoms have an equal number of protons and electrons This makes the atom

electrically neutral However, it is possible for an atom to gain or lose electrons If normal atom loses

one electron that means the atom has an extra proton Since there are more positive charges than

negative ones, the atom has a positive charge In case an atom gains an extra proton, the atom will

have a negative charge

The outermost orbital electrons are sometimes held very loosely to the nucleus like a distant planet

may be to the Sun Collisions may occur, which result in some electrons being driven from their

normal path and drifting through the material lattice These are called free electrons

Some atoms gain or lose electrons more easily than others The ones that do are the conductors

Copper atoms, for example, give up electrons very easily The atoms in materials such as plastic or

rubber do not give up electrons at all, which makes them excellent insulators

Conductor path

Figure 1-9 Free Electron

Fundamental question

Q1 Write correct answer to blank

Q2 All atoms made up of three particles What are they?

Q3 Which particles in the atoms gives rise to electric current

Q4 If we compare a thin conductor to a thick on, which is the better conductor?

Q5 If we compare two similarly thick conductors, but one is warm and others is cold, which of them is

the better conductor if current?

Q5 Select incorrect answer - ( )

1) Current of electricity is begun from movement free electron

2) If transfer of free electron is much, transfer of electricity is many (high current)

3) If free electron is seceded, electricity occurs

4) Atom has nature of material

2 Current, Voltage, Resistance

2.1 Current

Since free electrons are all negatively charged, they will all repel one another If there is a surplus

of electrons in one area and a shortage in another, electrons will flow toward the shortage - then

try to get away from each other When this movement happens, a flow or current of electrons is

created The current continues until the electrons have spread themselves out evenly

Current can be described as the rate of electron flow A measure of the amount of electron flow,

like a water pipe The larger pipe is greater capacity to carry flow

This meaning is that current flow much if electron's number moves much, so that water wheel's

moving becomes lively in picture below

Conclusively, electron's transfer is flowing of current, and can speak current intensity by electrons the

transfer amount

Current represent: The ampere is expressed using the letter I.The ampere describes the rate of flow

of electrons past any given point in a circuit

Current unit: A (Ampere)

1 Ampere: One ampere is equal to one coulomb of charge flowing part a point in one second

Current

Water level difference (Potential difference)

Water wheel Lamp

ON

Same

No potential Difference

2.2 Potential and potential difference VS Current

Let’s talk about more detail through water for the current

When a battery is connected to a lamp, it’s light up The current flow mean is because deference of

potential between + and -

This is because current flows through the lamp, this meaning is electron moving “–“ to “+” so, that

lamp “On” Then how and why current flows? Let’s talking a water wheel in the water tank as example

If no electronic current flows, the lamp will not light up and if there is no water flow, the water wheel

does not turn either Then, when will water flow in the example shown below?

When the water tank A and B are at the same water level water does not flow and the water wheel

does not turn

When there is water level difference between the two tanks, water flow from tank at higher level to the

tank at lower level since water is to flow from high to low level by nature As result, the water wheel

turns

The same is turn with electricity When is no potential difference current will not flow If there is

potential difference, current flows from higher potential to low one

As a result

The current is electric power

If transfer of free electron is much, it is meaning that electric power is big therefore heat generator a

lot

Water flow (Current flow) No water flow(No current flow)

Figure 2-2

When connect by wire between ＋ charge body and - charge body, electrons are moving and

neutralized At this time, heat generate by electron’s transfer

W t

Water tank A Water tank B

High water level

Low water level

Water wheel Water wheel does not work

No Water Flow

This heat occurrence function says that is 3 function of current

Heat function

If current passes, heat happens

Ex) cigar lighter, electric stove etc

Let’s talk about in the vehicle battery for current flow

The source of the electrical energy, the battery, contains two terminals, positive and negative From

our explanation of positive and negative charges, we can say that the atoms at the positive terminal

contain more protons than electrons This gives the positive terminal a positive charge On the other

side, atoms at the negative terminal have more electrons than protons As a result, that terminal has a

negative charge

The negative terminal has a tremendous supply of free electrons All these electrons, confined to a

small area, are repelling each other trying to get away

Summary for current

Flowing of current is transfer of electron

If transfer of electron is much, mean that current passes much

Though there is potential difference, current passes when connected between high

and low potential

If transfer of free electron is much, heats generate, Therefore, electric wire bunt out

that is done because so much current passed

Quantity of current can explain by quantity of water that passes a pipe

Current passes much to some actuator means that amount of electric power is strong

2.3 Voltage

If different electrical nature connects other two charged bodies by wire, current passes, because it is

difference of electric potential between two charged bodies that current passage

It is known that this electrical difference is electric potential

It is known that advance guard's difference is voltage

Because there is electric potential difference, occur electromotive force

The volt (V) is the electrical unit used to express the amount of electrical pressure present, or the

amount of electrical force produced by chemical action inside the battery

Voltage Symbol: E, Voltage unit: V

1 volt: When 1 coulombs' electric charge moves to charged body and work 1joule, for two point

charged bodies between potential differences

2.4 Potential & Potential Difference VS Voltage

Voltage can be expressed by potential and potential difference Figure 2-3 explains how these are

related to each other, referring to water tank When the two water tanks are connected by pipe, water

will flow from the tank of higher water level to the tank of lower level The water level has been

measured with reference to ground Similarly, potential is measured related to certain standard level,

which is called earth or ground, and the potential of earth (ground) is taken as 0 (V) Usually the

physical earth is taken as the ground but in the case of automobiles the negative (－) terminal of

battery is taken as the ground The water level of the lower tank is taken as the reference (water level

“0”) In case of the battery, 12 volts means the potential difference between the two terminals of the

battery

Figure 2-3 Potential & potential difference

Water level difference (Potential difference)

Water current (Electrical current)

If open valve in above Fig.2-3, because position of water is different, water is flowed water tank “A” to

water tank “B”

But, if it is no difference position (or pressure), water does not flow even if opened valve

That is, if difference of pressure becomes same, current means stagnant

Therefore, because it is no flowing of current, actuator is not working, and there is no heat occurrence

by current

If, so difference pressure of the between tank “A” and “B”, pipe is burst and heat occurrence

Meaning positive is 12volts and negative means that is 0volt in Battery of passenger car

Thus, difference of electrical potential is 12 in battery of passenger car

This meaning positive (+) is 12 volts and negative (-) means 0volt

If close switch in below figure 2-4, because current is passed, lamp may become “ON”

Voltage of each position according to ON or OFF switch, become different in below fig 2-4

It is same with as follow

Figure 2-4 Potential & potential difference

Voltage of each position

Voltage measure position Switch OFF condition

(Lamp OFF)

Switch ON condition (Lamp ON)

+(Positive)

12 Volt BATTERY

Although voltage between E and F are 12volts because resistance is infinity before switch closed,

switch if do closed resistance because to 0 ohm’s become 0 volt

And, current passes when switch closed, at this time, voltage between D and A become 0 volts

because resistance is 0

Also, while current is flowing, voltage between C and D are 12volt, however, switch off if is done

become nothing volt

As a result, important is thing while flowing current, voltage between “B” and “C” are 12volt, and

voltage between “D” and “A” are become 0 volts

How many voltage each other position at below circuit?

Condition 1 : before room lamp switch on.(Lamp OFF)

Q1 Voltage measure position between “C40-1” and “Battery earth” ( ) volt

Q2 Voltage measure position between “C40-2” and “G9” ( ) volt

Q3 Voltage measure position between “R25” and “R26” ( ) volt

Condition 1 : after room lamp switch on.(Lamp ON)

Q1 Voltage measure position between “Battery positive” and “R25” ( ) volt

Q2 Voltage measure position between “R25” and “Battery earth” ( ) volt

Q3 Voltage measure position between “R26” and “Battery earth” ( ) volt

FUSE F8 5A

C224

BATTERY COMPARTMENT FUSE BOX

C40-2

CR02

R25

R26 ROOM LAMP

G09

12 Volt Battery

Battery earth

Battery + Battery -

2.5 Resistance

If free electron moves on interior of some material, because electrons have electrical nature, become

flowing of current That is current studied already that 1 ampere passes if 6.28*10E+18's electron

move during 1 second follow in number of electron to move per unit time

By the way, all kinds of materials are composed of atoms and after all, these are an obstacle for free

electrons to move inside among them

It is called Electric Resistance to prevent the movement of electron

So, the electric resistance in a material is changed according to the following variables:

- Kind of material

- Sectional area of wire

- Length of wire

- Temperature

Also, all materials have different kind of structure of atoms

Therefore, the environment for free electrons to move in the materials is various in any kind of

material

Thus, even if the electrons of same quantity are engaged, the amount of electrons, which can pass

through the narrow space per unit time, can be change

And, when the thickness become big in same material, the passageway, that electrons can move is

getting wider

In addition, if transfer distance of electron is long, it takes much time for electron to move in the

passageway

Therefore, the amount of electron that moves within unit time can be decreased

This means that there are many electric resistances

Now, the formula that expresses the electric resistance is as follows:

Also, if temperature of most material rises, motions of atom liveliness get worn out

Therefore, these atoms can be obstacle to free electrons of their movement

So, electric resistance of material increases temperature rises on the whole

Expression of resistance: R

Unit of resistance : Ω(ohm)

Symbol of resistance:

※1 ohm: Resistance value of when supplied 1volt to conductor and current of 1 ampere flowing

2.6 Conductor, insulator and resistor

If electrical current flows easily through a material, that material is called a conductor Metals such as

copper, silver, gold, aluminum, and steel are used as paths in automobiles because they are good

conductors Copper is used almost exclusively in wires because of its durability and cost

The opposite of a conductor is an insulator Insulators do not allow current to flow through them

Glass, plastic, rubber, and ceramics are good insulating materials The plastic coating on the outside

of a wire is an example of an insulator

When free electron moves on conductor interior,

Some electrons collide with atoms and part of kinetic energy emits as light or heat

Thereby, generator heat called Joule heat

The generator heat is proportional with square of current and in size of resistance

Joule heat = Square of current×Resistance

Utensils that to use Joule heat

Copper Iron Steel Aluminum Silver Tin Damp earth

Insulators Conductors

2.7 Current, Voltage, and Resistance relation

Current, voltage, and resistance determine how electricity will behave in a circuit These three

characteristics are closely related When one changes, it immediately causes one or both of the

others to change as well The relationships between current, voltage, and resistance can be

expressed with a set of mathematical formulas The formulas are part of a set of rules called Ohm’s

Law These rules can be used to explain or predict the behavior of electricity in all types of circuits

Current: A measure of the amount of electron flow Like a water pipe, the larger the pipe the

greater the capacity to carry flow

Measured in “Amperes”, or “Amps” (A)

Voltage: A measure of the potential of a source to supply electromotive force (EMF), or

electrical pressure

Measured in Volts (V)

Resistance: A measure of the opposition to current flow in a circuit

Measured in Ohms (Ω)

Explain more through figure below

- If pump operates, water circulates for clockwise direction

- Operation pressure of motor is 12kg/cm2

- At this time, actuator working 100% moving

- Between pump and actuator: 12kg/cm2

- Between actuator and pump: 0kg/cm2

P actuator

Condition 2

When there is resistance between P1 and P2 in circuit, pressure of each position.

P1 = 12kg/cm2

P2 = P1 – R1 (Quantity which pressure of water is been blocked by R1)

R1 (Quantity which pressure of water is been blocked by R1) = Pump (or P1) – P actuator

P2 = P actuator (Apply pressure to the actuator)

P actuator = P2 – Pa

Pa = Pb = 0kg/cm2

※Pressure

- Between pump and actuator: 12kg/cm2 (pump pressure) - R1

- Between P1 and P2: Pressure is drop as much as quantity, which is been blocked by R1

- Between actuator and pump: 0kg/cm2

As a result pressure is trembled as quantity, which is been blocked by resistance

- Between actuator and pump: Pressure is drop as much as quantity, which is been blocked by R2

- Between Pb and pump: 0kg/cm2

When is normally, pressure between actuator and B is pump

By the way, if there is resistance between actuator and pump, pressure does not drop to zero as the

Current, Voltage and Resistance summary

Voltage

- If there is electric potential, electron's transfer is begun

- Thus, flowing of current is begun

- If voltage is high, electrons transfer much have

-Thus, The flowing of current becomes much

Current

- Current is transfer amount of free electron

- Current operates electric actuators

- If voltage is high, current flow much But, overheat if flowing of current exceeds

- Resistance disturbs flowing of current Thus, if resistance is high, flowing of current is

decreased

- If current passes excessively, heat occurrence

- A magnetic field occurs around wiring that when current passes

Resistance

- Resistance disturbs of free electron flowing Thus, disturb flowing of current

- If there is much resistances, electricity actuator of 100% does not operate

Because, It is current 100% does not pass

- Resistance is started aging or degradation of wiring in wire harness

- Electricity problem is begun from resistance in a car

They are contact resistance of connector, disconnect of connector, poor ground

Voltage

Current

Resistance

2.8 Direct & Parallel current Circuit

Basically, an automobile uses DC (Direct Current) electric source, but electric circuit is consist

of series current circuit, parallel current circuit, and series/parallel current circuit

Therefore, the major electric circuit of automobile is series/parallel circuit

2.8.1 Direct current circuit (Series circuit)

A typical complete circuit contains an energy supply, circuit protection, a load, some kind of control,

and a path When a conductor connects all of these components end-to-end, the result is called a

series circuit

When batteries are connected in series (end-to-end), the total output voltage equals the sum of all the

individual battery voltages Although this set-up provides a higher output voltage, their combined

capacity to supply current is the same as that of a single cell

Namely, resistance or power source is connecting method is linked by series, and circuit

composition that is linked to resistance is same with Fig 2-6 below

Fig 2-6 Direct current circuit

R1

I1 I2 E

Direct circuit of equivalence Direct circuit of 2 lamps

Total battery voltage

1.5 volt × 4 batteries = 6 volt

Total battery voltage

12 volt × 2 batteries = 24 volt

Fig 2-5 Series connect in batteries

Several resistances of connection of resistance compose by series, become in one resistance form

E = I R = I (R1 + R2)

In this formula, (R1 + R2) says that is equivalence resistance or combined resistance and combined

resistance increases is many if there is much resistances

However, value of current is decrease relatively

※ To calculation total resistance in series circuit

Total resistance “R” = Sum of all resistances of circuit (R1 + R2 - R9)

There are common characteristics to all direct current circuits: Summary for direct current

□ There is a single path for current

□ The same amount of current flows through every component

□ An open at any point prevents current flow

□ At series connection of resistance, total resistance increases connect resistance

□ Total resistance increases, flowing current decreases in circuit

□ Flowing current is always same in series circuit even if measure in any place

1) Circuit with load in direct-current circuit

Fig 2-8 Direct current circuit

2) To calculate both end voltage of resistance in D.C circuit - 1

- What is the total resistance in below circuit?

R1 R0

I

V

Fig 2-7 Direct current circuit

- What is the current in below circuit?

- What are the individual voltages of E1, E2, E3 in picture below?

E = 2volt + 4volt + 6volt = 12 Volt

3) To yield both end voltage of resistance in D.C circuit - 1

Sum of variable resistance is 20 kΩ between x and z in

below circuit

In case resistance of between x and y is 5 kΩ

3-1) How much V0 volt?

3-2) How much volt between x and y?

3-3) E = (x ~ y volt) + V0 volt = [ ] Volt

Direct current

Moving charges give rise to a current “I” whose strength is measured in ampere

The direction of flow and magnitude of direct current are independent of time

Direction of current flow and measurement

Current flowing from positive pole to negative pole outside current source is designated as positive(in

reality, the electronic travel from the negative to the positive pole)

An ampere meter in the current path measures current flow : Voltage is measured by a voltmeter

Current measurement in direct current circuit : Series connected voltage meter

2.8.2 Parallel current circuit (Parallel circuit)

In a parallel circuit, there is more than one path for current to flow Each current path is called a

branch Branches are connected to one common positive and one common negative terminal;

therefore, the voltage applied to each branch is the same

When batteries of the same voltage are connected in parallel, the total output voltage is the same as

for any single battery However, since current flows from all the batteries simultaneously, this

arrangement will supply a larger current

The illumination system in an instrument cluster is a good example of a parallel circuit If one lamp

burns out or is removed the others will still work

+ -

Ampere meterA

Fig 2-11 Parallel circuit

1) First, must know resistance value to know flowing current in parallel circuit

Therefore below formula is formed

E = E1 = E3

E = I R

Rtotal = 1 ÷ (1/R1 + 1/R2) = 1 ÷ (R2 + R1) / R1 × R2

★To calculate easily total resistance

R total = Multiplication of resistance ÷ Sum of resistance

3) Also, whole current I is same with sum of current that each 3 lamp consumes in circuit

4) When each switch did “ON”, to each light bulb flowing current

I 2E2

Fig 2-12 Parallel circuit

5) There are two common characteristics to all parallel circuits:

　 The total current in the circuit equals the sum of the branch currents

Therefore, resistance values of current according to addition or delete change

　 An open in one branch affects only the load in that branch; other branches continue to operate

normally

Current in parallel circuit is different according to point that measure

That is, when measure current in above circuit of right hand side

A point current = (I 1+I 2+I 3) = B point current

Point C, D, E current: Current that each lamp consumes

If connect batteries by parallel circuit, voltage are fixed, but current consumes becomes more per

In formula E1 = R1 I2, I1 = E/R1 = [ ] A

In formula E2 = R2 I2, I2 = E/R2 = [ ] A

Fig 2-13 Parallel circuit

2.8.3 Series - Parallel Circuit

A series-parallel circuit combines both series and parallel circuits, along with their respective

characteristics The first step in analyzing a series-parallel is to break the circuit down to its simplest

form Then analyze only the particular series or parallel circuit characteristics that apply to that

component

That is, composition of car circuit belongs to series-parallel circuit as circuit that series and parallel

are mixed

1) Equivalent circuit of figure “A” is circuit that series and parallel are mixed, and figure “B” R1.2 is

combined resistance value of R1+R2 of figure “A” that figure “B” circuit diagram computation

combined resistance of parallel resistance R1 R2 of figure “A” and represent by equivalent circuit of

series

2) Because current I is increased according as parallel resistance increases in this circuit, can be

represent by total resistance of I=/R1,2 + R3

3) Whole combined resistance “R” of this circuit

- Combined resistance of between a and b = (R1×R2) / (R1+R2) ohm R1,2

- Combined resistance of between a and c= R1,2 + R3 ohm - R (Combined resistance)

4) Whole circuit current I

7) Current flowing when switch ON In below circuit At this time

1.How much resistance of each lamp?

2.How much combined resistance between “a” and “b”?

3 All current I?

4.How much voltage between “a” and “b”?

5.How much voltage between “b” and “c”?

Here, when lamp ON temperature ignores of lamp

3.Ohm’s Law

Any operating electrical circuits must have three factors, voltage, current, and resistance Their

relationship can be described by Ohm’s Law statement:

“The amount of current that will flow in any circuit is directly proportional to voltage and inversely

proportional to resistance.”

In other words, as voltage goes up, current goes up, but as resistance goes up current goes down

VOLTAGE (V) CURRENT (A) RESISTANCE (Ω)

SAME UP DOWN SAME DOWN UP

Ohm’s Law is the basis for electrical troubleshooting Taken as a statement, Ohm’s Law expresses

the characteristics that govern electrical behaviors in a circuit However, Ohm’s Law can also be

expressed as an equation Using this equation, calculating a specific value for any three electrical

factors is possible:

　 How much current, if voltage and resistance are known

　 How much voltage, if current and resistance are known

　 How much resistance, if voltage and current are known

When you know any two values, you can use Ohm’s Law equation to calculate the third value

As, previously discussed, single letters of the alphabet are used to represent current, voltage, and

resistance; current by the letter I for intensity; voltage by either V or an E for electromotive force; and

resistance by the letter R

Ohm’s Law circle

A handy memory tool is the Ohm’s Law circle

If you hold your finger over the letter of the unknown value, the correct formula stands out

For example, to solve for I, place your finger over that letter and the correct formula is seen to be:

The circuit on the right shows the values of the voltage and the resistance To determine the current,

we merely substitute the unknown value into the formula:

I = E / R

I = 12 volt / 6 ohms

I = 2 Amperes

According to the Ohm’s law, when the voltage increases, so does the current To prove this, let’s look

at the same circuit we just did, but only this time we’ll double the voltage

We still use the same formula as before

Fig 3-3 Ohms law current 2

Notice that when the voltage doubles, the current also doubles We expect this because current is

DIRECTLY PROPORTIONAL to voltage as Ohm’s Law states

That statement also says that current is INVERSELY PROPORTIONAL to resistance So, let’s find out

Again, using the same circuit, only this time we’ll double the resistance

3.3 Determining Voltage

The formula to determine voltage is the easiest of the three Voltage = current times the resistance

The circuit on the right shows us there is 2 amps of current and 3 ohms of resistance Therefore:

E = I × R

E = 4 × 3

E = 12 volts

3.4.1 Voltage Drop 1

The voltage removed from the circuit by the load (light bulb, motor, incorrect wire size, etc.) is called

the voltage drop The total voltage lost must equal the voltage applied The amount of this loss can be

calculated by using the formula we studied,

V = I × R

In practical terms, if you have a simple circuit that consists of a source (the battery) and a load (a

lamp), the voltage drop across the lamp is determined by the amount of current times the resistance

R2R1

3.4.2 Voltage drop 2

If current flows in the load (resistance) of circuit, voltage drops as much as impressed electromotive

force in the load (resistance) In other word, exhausted voltage is same with impressed voltage in

resistance When switch turned “ON” in below circuit As 12volt's voltage are supplied to this circuit

and lamp is operated, current that consume in lamp passed

At this time, the voltage drop as much impressed volt in both side of the lamp between “+” and “-“

This is voltage drop

By the way, if there is some contact resistance in S/W contact point, flowing current and lamp voltage

drop as much S/W contact point resistance to lamp Thus, it means that the current and voltage drop

caused by the contact resistance of S/W are moved from lamp to S/W contact point

If summarize, when actuator (lamp, motor, solenoid, etc) operates, must be happen to actuator

Impressed voltage = Voltage drop from actuator

While current flowing, if there is not same voltage between impressed voltage and voltage drop from

actuator, meaning that resistance located in circuit, such as switch, wire, ground point battery terminal

This is a kind of very important theory to repair the vehicle

3.5 To understand voltage drop in equivalent circuit

Earth

V2 Voltage When switch “ON” 12 Volt in normality

If lower than 12Volt, the lamp does not work normality because it means that resistance exists somewhere

12VOLT

BATT

SWITCH LAMP

V1 Voltage when SW Off = 12Voltwhen SW ON =0 Volt

Fig 3-7 Voltage drop 1

V4 12volt

12

VOLT

G1

V1 8volt

V24volt

1) In above circuit, when switch turned “ON”, the current flowing through R1 and R2

At this time, V3 is12 volts before switch turned “ON”

However, V3 is 0 volt, when switch turned “ON”

2) If V1's voltage is 8 volt, it is voltage drop 8 volt in R1

At this time, V2's voltage become “12 - 8 = 4 volt”, because battery voltage is 12Volt

Also, because expressed as "V1(voltage drop of R1) = I (Total current of circuit) × R1(R1

resistance)"

R1's voltage drop and R2's voltage drop are inverse proportion each other

3) If R1's voltage drop rise, R2's voltage drop reduced relatively

4)Sum of voltage drop of R1 and R2 is same with Battery applied voltage

5)When current passes, if resistance does not exist, voltage is 0 volt

4 Kirchoff’s Law

Electric circuits are divided into series circuit, parallel circuit and series/parallel circuit according to

connecting method The sum of input current and output current are equal in this circuit

Also, impressed voltage and sum of voltage drop is same, this is Kirchoff’s law

There are two laws in Kirchoff's law

4.1 Kirchoff’s current law (Kirchoff’s first law)

In circuit inflow current's sum and outflow sum of done current same

Inflow current – outflow current = 0

In this current flow below formula is formed in below circuit

Written as a formula:

I1+I4 (INPUT CURRENT) = I2+I3+I5 (OUTPUT CURRENT)

Law of Kirchoff’s current in circuit diagram

I1 = INI5 = OUT

I2 = OUT

I3 = OUTI4 = IN

Fig 4-1 Kirchoff’s current

Fig 4-2 Kirchoff’s current law 2

4.2 Kirchoff’s voltage law (Kirchoff’s second law)

The source voltage of a series circuit is equal to the total value of each individual voltage drop, and

sum of voltage drop and sum of applied voltage big number are 0 (Zero)

Input source voltage – Sum of voltage drop = 0

1) When flow current in below circuit, voltage drop occurrence in resistance R1 and R2

2)This voltage drop is proportional in resistance value of each resistance

3)Sum of voltage drop that is occurrence in each resistance is same with applied voltage

4) Kirchoff’s voltage law material for exercise

Value of resistance R1 and R2 is different in this picture

Current is 4A and value of voltage drop is 8Volt in resistance R1

How many voltage drops from R2?

12Volt(power source) - 8Volt(R1 voltage drop) = 4Volt

I

12 Volt

Fig 4-3 Kirchoff’s voltage law 2