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EE201 Fundamentals of Electric Circuits

Instructor:Dr. Ali M. Eltamaly, Office: 2C20, [email protected]

Phone: 4676-828Website: faculty.ksu.edu.sa/eltamaly

Text Book:Introductory Circuit Analysis By Robert L. Boylestad, 10th Edition, Published by Prentice Hall, 2001.

Mid term tests:First mid-term Exam: Tuesday, 22/11/1430 H (10/11/2009)Second Mid-Term Exam: Sunday, 26/12/1430 H (13/12/2009)Third Mid-Term Exam: Tuesday, 26 /1/1431 H (12/1/2010)

Notes:1. The best two mid-term exams will be counted2 All id t ill b f d ft M h b

Grading Policy:

2. All mid-term exams will be performed after Maghreb prayers3. If you miss any mid-term exam, there will be no make up test for any given reasons

g yMid-Term Exams: 50%Home Works + Quizzes 10%Final Exam 40%

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Topic Chapters

Definitions and Laws 1-4

Course outline:

Series/Parallel (DC) circuits analysis

5-8

Network Theorems (DC) circuits 9

Sinusoidal alternating and phasors 13-14

S i /P ll l (AC) i it 15 17Series/Parallel (AC) circuits analysis

15-17

Network Theorems (AC) circuits 18Network Theorems (AC) circuits 18

Power (AC) 19( )

Polyphase Systems 22

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FIG. 1.5 Texas Instruments TI-89 calculator.

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POWERSOFTEN

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Chapter2Current and Voltage

ATOMSANDTHEIRSTRUCTURE

CurrentandVoltage

FIG. 2.1 Hydrogen and helium atoms.

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Shellsandsubshells oftheatomicstructure.

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The atomic structure of copper.

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CURRENT

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If 6.242 * 1018 electrons drift at uniform velocity through the imaginary circular cross section of Fig. 2.7 in 1 second, the flow of charge, or current, is said to be 1 ampere (A)sec o o g. .7 seco d, e ow o c a ge, o cu e , s sa d o be a pe e ( )

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VOLTAGE

A potential difference of 1 volt (V) exists between two points if 1 joule (J) of energy is exchanged in moving 1 coulomb (C) of charge between the two points.

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Potential: The voltage at a point with respect to another point in theelectrical system. Typically the reference point is ground, which is atzero potential.zero potential.

Potential difference: The algebraic difference in potential (or voltage)between two points of a network Voltage: When isolated like potentialbetween two points of a network. Voltage: When isolated, like potential,the voltage at a point with respect to some reference such as ground (0V).

Voltage difference: The algebraic difference in voltage (or potential)between two points of the system. A voltage drop or rise is as thebetween two points of the system. A voltage drop or rise is as theterminology would suggest.

Electromotive force (emf): The force that establishes the flow ofElectromotive force (emf): The force that establishes the flow ofcharge (or current) in a system due to the application of a difference inpotential. This term is not applied that often in todays literaturebut isassociated primarily with sources of energy.

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3 1 Introduction3.1 Introduction The resistance of any material with a uniform cross-sectional area is

determined by the following factors: Material Length Cross-sectional AreaCross-sectional Area Temperature

FIG. 3.1 Resistance symbol and notation.

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Film resistors: (a) construction; (b) types.

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Molded composition-type potentiometer.

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FIG. 3.25 Color coding for fixed resistors.

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Color coding.

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FIG. 3.27 Example 3.13.

3 = k1210*12 3Dr

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FIG. 3.29 Five-band color coding for fixed resistors.

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Chapter4 OhmsLaw,PowerandEnergy

Developed in 1827 by Georg Simon Ohm

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OhmsLaw

EI =R

I =

Where: I=current(amperes,A)

E=voltage(volts,V)

R=resistance(ohms,)

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FIG. 4.3 Defining polarities.

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4 4 Power4.4 Power

F Powerisanindicationofhowmuchwork(theconversionofenergyfromoneformto( gyanother)canbedoneinaspecificamountoftime;thatis,arate ofdoingwork.; , g

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PowerPower

WtWP =t

second / joule 1 (W)Watt 1 =FPowercanbedeliveredorabsorbedasdefinedby

th l it f th lt d th di ti f th

j( )

thepolarityofthevoltageandthedirectionofthecurrent.

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4 5 Energy4.5 Energy

F Energy(W)lostorgainedbyanysystemisdeterminedby:y

W= Pt

F Sincepowerismeasuredinwatts(orjoulespersecond)andtimeinseconds,theunitofenergyisthewattsecond (Ws)orjoule (J)

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EnergyEnergy

The wattsecond is too small a quantity for mostThewatt secondistoosmallaquantityformostpracticalpurposes,sothewatthour (Wh)and

kilowatthour (kWh)aredefinedasfollows:

(h) time (W) power(h) time (W) power (Wh)Energy =

1000(h) time (W) power(kWh)Energy =

Thekillowatthourmeter isaninstrumentusedformeasuringtheenergysuppliedtoa

id i l i l f l i iresidentialorcommercialuserofelectricity.

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4 6 Efficiency4.6 Efficiency

FEfficiency()ofasystemisdeterminedbythefollowingequation:g q

= Po /Pi:Where=efficiency(decimalnumber)

Po =poweroutput

Pi =powerinputDr

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Chapter 5 Series dc CircuitsFIG. 5.4 Series connection of resistors.

NT RRRRRR +++++= ...4321FWhen series resistors have the same value

NRRT =Dr

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FIG. 5.5 Configuration in which none of the resistors are in series.

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FIG. 5.6 Series connection of resistors for Example 5.1.

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FIG. 5.12 Schematic representation for a dc series circuit.

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5.5 VoltageSourcesinSeries

F Voltage sources can be connected in series to increase or decrease the total voltage applied to the system.g pp yF Net voltage is determined by summing the sources

having the same polarity and subtracting the total of the sources having the opposite polarity.

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KirchhoffsVoltageLaw

F Theappliedvoltageofaseriescircuitequalsthesumofthevoltagedropsacrosstheseriesg pelements:

= dropsrises VVFThesumoftherisesaroundaclosedloopmustequalthe sum of the drops.

dropsrisesthesumofthedrops.

FWhenapplyingKirchhoffsvoltagelaw,besuretoconcentrateonthepolaritiesofthevoltageriseordropth th th t f l tratherthanonthetypeofelement.

F Donottreatavoltagedropacrossaresistiveelementdifferentlyfromavoltagedropacrossasource.

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FIG. 5.26 Applying Kirchhoffs voltage law to a series dc circuit.

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EXAMPLE5.4Determine the unknown voltages for the networks of Fig. 5.14.

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EXAMPLE 5.5 Find V1 and V2 for the network of Fig. 5.15

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NotationFDoublesubscriptnotationF Becausevoltageisanacrossvariableandexistsb i h d bl b i ibetweentwopoints,thedoublesubscriptnotationdefinesdifferencesinpotential.F ThedoublesubscriptnotationVab specifiespointaasF abthehigherpotential.Ifthisisnotthecase,anegativesignmustbeassociatedwiththemagnitudeofVab .F The voltage V b is the voltage at point (a) with respectF ThevoltageVab isthevoltageatpoint(a) withrespecttopoint(b). Dr

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Notation

F SinglesubscriptnotationF The single subscript notation V specifies theF ThesinglesubscriptnotationVa specifiesthevoltageatpointa withrespecttoground(zerovolts).Ifthevoltageislessthanzerovolts,anegativesignmustbeassociatedwiththemagnitudeofVa .

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NotationNotation

F GeneralRelationshipF Ifthevoltageatpointsa andb areknownF g pwithrespecttoground,thenthevoltageVabcanbedeterminedusingthefollowingequation:

Vab =Va VbDr

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5 7 Voltage Division in a Series Circuit5.7 VoltageDivisioninaSeriesCircuit

F Thevoltageacrosstheresistiveelementswilldivideasthemagnitudeoftheresistancelevels.F Thegreaterthevalueofaresistorinaseriescircuit,themoreoftheappliedvoltageitwillcapture.

FV lt Di id R l (VDR)FVoltageDividerRule(VDR)FTheVDRpermitsdeterminingthevoltagelevelsofacircuit without first finding the current.circuitwithoutfirstfindingthecurrent.

ERV =T

XX RRV =Dr

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Chapter6 ParalleldcCircuits

FTwoelements,branches,orcircuitsareinparalleliftheyhavetwopointsincommonasinthefigurebelow

Insert Fig Insert Fig 66..22

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GGGGG NT GGGGG ++++= ...321TR

1=N

T

RRRR

R 1...111321

++++

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EXAMPLE 6.3 Determine the total resistance for the network of Fig. 6.8.

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Parallel ResistorsParallelResistors

FF l i i ll lFForequalresistorsinparallel:

WhereN=thenumberofparallelresistors.

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EXAMPLE6.4

FindthetotalresistanceofthenetworkofFig.6.9.

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EXAMPLE6.4CalculatethetotalresistanceforthenetworkofFig.6.10.

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ParallelResistors

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EXAMPLE 6.7 Calculate the total resistance of the parallel network of Fig. 6.13.

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EXAMPLE 6.8 Determine the value of R2 in Fig. 6.15 to establish a total resistance of 9 k.

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6.3 ParallelCircuitsF Voltage is always the same across parallel elements.V1 = V2 = E

The voltage across resistor 1 equals the voltage across resistor 2, and both equal g q g , qthe voltage supplies by the source.

III 21 IIIs +=EE

2121 R

EREIIIs +=+=

21

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EXAMPLE 6.12 Given the information provided in Fig. 6.23:

a. Determine R3.b. Calculate E.c. Find Is.d. Find I2.

D i Pe. Determine P2.

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Kirchhoffs Current LawKirchhoff sCurrentLawF Most common application of the law will be at the junction of two or

h fmore paths of current.F Determining whether a current is entering or leaving a junction is sometimes the most difficult task.FIf the current arrow points toward the junction, the current is entering the junction.F If the current arrow points away from the junction, the current is leaving the junction.

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EXAMPLE 6.15 Determine the currents I3 and I5 of Fig. 6.29 through applicationsof Kirchhoffs current law.

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6.6CURRENTDIVIDERRULE

TT IRVI ==xx

x RRI ==

TT

x IRRI = T

xx R

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EXAMPLE 6.17 Determine the current I2 for the network of Fig. 6.35 using the current divider rule.

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EXAMPLE 6.18 Find the current I1 for the network of Fig. 6.36.

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Currentseeksthepathofleastresistance.

RT

x

Tx IR

RI =

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OPENANDSHORTCIRCUITS

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Determine the unknown voltage and current for each network of Fig. 6.48.

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EXAMPLE 6.25 Determine V and I for the network of Fig. 6.52 if theresistor R2 is shorted out.

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