Solution Manual for Delmar's Standard Textbook of Electricity, 5th Edition

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’s Guideto AccompanyDELMAR’S STANDARD TEXTBOOKOF ELECTRICITYFifth EditionbyStephen L. HermanandKerry A. ReinhackelSOLUTIONSGUIDE

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iiiContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vSection 1Safety, Basic Electricity, and Ohm’s Law. . . . . . . . . . . . . . . . . . . . . . . .1Unit 1Atomic Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Unit 2Electrical Quantities and Ohm’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Unit 3Static Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Unit 4Magnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Unit 5Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Section 2Basic Electric Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Unit 6Series Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Unit 7Parallel Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Unit 8Combination Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Unit 9Kirchhoff’s Laws, Thevenin’s, Norton’s, and Superposition Theorems. . . . .20Section 3Meters and Wire Sizes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Unit 10Measuring Instruments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Unit 11Using Wire Tables and Determining Conductor Sizes. . . . . . . . . . . . . . . . .27Section 4Small Sources of Electricity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Unit 12Conduction in Liquids and Gases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Unit 13Batteries and Other Sources of Electricity. . . . . . . . . . . . . . . . . . . . . . . . . .32Unit 14Magnetic Induction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35Section 5Basics of Alternating Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38Unit 15Basic Trigonometry and Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38Unit 16Alternating Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Section 6Alternating Current (AC) Circuits Containing Inductance. . . . . . . . . .43Unit 17Inductance in AC Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43Unit 18Resistive-Inductive Series Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45Unit 19Resistive-Inductive Parallel Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47

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ivSection 7AC Circuits Containing Capacitors. . . . . . . . . . . . . . . . . . . . . . . . . . .50Unit 20Capacitors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50Unit 21Capacitance in AC Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54Unit 22Resistive-Capacitive Series Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56Unit 23Resistive-Capacitive Parallel Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57Section 8AC Circuits Containing Resistance-Inductance-Capacitance. . . . . . . .61Unit 24Resistive-Inductive-Capacitive Series Circuits . . . . . . . . . . . . . . . . . . . . . . . .61Unit 25Resistive-Inductive-Capacitive Parallel Circuits. . . . . . . . . . . . . . . . . . . . . .64Unit 26Filters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67Section 9Three-Phase Power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69Unit 27Three-Phase Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69Section 10Transformers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72Unit 28Single-Phase Transformers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72Unit 29Three-Phase Transformers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76Section 11DC Machines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80Unit 30DC Generators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80Unit 31DC Motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83Section 12AC Machines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87Unit 32Three-Phase Alternators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87Unit 33Three-Phase Motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89Unit 34Single-Phase Motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93Answers to Review Questions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108Answers to Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133

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vThis’s Guide has been divided into fivemain sections to help you in the instruction process. Thefirst section is an overview of instruction techniques andinformation on learner types. The second section in-cludes teaching instructions for each of the 34 units ofthe text. The third section includes answers and solu-tions to the review questions. The fourth section con-tains 15 tests that can be used at various intervals in theinstruction process. The final section includes answersto the tests.This lesson plan manual has been written with theidea that many of the instructors usingDelmar’s Stan-dard Textbook of Electricityhave not had an opportu-nity to take a course in education. With this in mind, avariety of ideas to help the instructor teach the materialhas been written into the section-by-section lesson plans.Additionally, this introduction will give the instructor abrief overview of the four main types of learners andways to enable those types of learners to be successfulin the classroom. This success in the classroom will,ultimately, lead to success out in the field.There are four basic types of learning strategies thatmost people use to learn new material. Some individualsmay use more than one of these strategies, but most willuse at least one, whether they are aware of it or not. Thefirst type I will discuss is the visual learner.Visual learners use what they see to help them under-stand what is being taught. This goes beyond just read-ing a text. In fact, visual learners may not benefit asmuch from the printed word as they do from pictures,graphs, charts, and other examples drawnaboutwhat iswritten in the text. For this type of learner there are in-structions concerning visual aids throughout this entiremanual. Many people are visual learners, often in com-bination with one or more of the other learning styles,such as audile.An audile learner will listen carefully to everythingthe instructor has to say. Depending on the memory ca-pabilities of this type of learner, he or she may also takequite a few notes. This type of learner may ask for in-formation or explanations to be repeated, or restated ina different way. If this individual also uses the strategiesof the visual learner, then explanations that are simple,clear, and are accompanied by visual aids benefit themthe most. They may do just fine right where they sit. Forthe kinesthetic learner, though, this may not be the case.A kinesthetic learner is a hands-on type of learner.These individuals like to hold the visual aids in theirhands and work things out (like experiments) with theirhands. They will want to create a circuit and connect thewires, resistors, and so on. They will also benefit, as willthe visual learners, from drawing their own circuits anddiagrams. They may or may not be good at compre-hending the material just from reading the text, as tactilelearners will be.Tactile learners are good readers and can compre-hend most of the material that they need to learn byreading the text. Tactile learners, however, will alsogreatly benefit from the use of visual aids, hands-onactivities, and clear concise explanations.As often as possible, the instructor should try to fol-low the lesson plans, bring in visual aids, make charts,and use the discussions to uncover any prior knowledgethat students may have about each unit.Individuals learn better when they believe that theyalready have some knowledge on a subject that they arebeginning to study. With this in mind, each unit has astatement that calls for a question/discussion time thatwill include allowing students to realize that they prob-ably are much more familiar with the overall subjectmatter than they thought they were. Think of it as wall-paper being hung on a wall. The wallpaper simply sticksbetter, and more readily, if there is already some paste orglue on the wall. Our minds are the same way. This priorknowledge, uncovered and made known to a student, isthe glue that gives your lesson something to stick to. Itsticks better, faster, and more readily when the studenthas been made aware that the glue is there. The slight-est amount of glue is always going to hold somethingbetter than no glue at all.Each unit is completed with a Unit Round Up sec-tion. This is where you will always need to double-checkfor understanding. Just in case the glue didn’t hold, andyour lesson slid off onto the floor, you will have studentsIntroduction

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viexplain concepts to you, work out formulas, and explainwhy the various things work as they do. The best way tocheck for understanding is to have the students give backto you, in their own words, what you have given to them.In the case of the various formulas, practice is the key. Itwill be useful if you can create some problems of yourown for your students to solve, using the formulas thatare being covered in any given unit.This manual was written with you in mind. It has beenwritten in user-friendly language and is meant to be abenefit and aid to you as a teacher. Obviously, any ideathat has been given as a lesson enhancer is optional. Everylearning group is different, and one group may requireeverything you can come up with to help them grasp thematerial, and other groups may barely require your pres-ence! Use what will help you and pass over what will not.

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1SECTION 1Safety, Basic Electricity, and Ohm’s LawOUTLINES-1General Safety RulesS-2Effects of Electric Current on the BodyS-3On the JobS-4Protective ClothingS-5Ladders and ScaffoldsS-6FiresS-7Ground-Fault Circuit InterruptersS-8GroundingKEY TERMSMeterDe-energized circuitIdiot proofingHorseplayArtificial respirationCardiopulmonary resuscitationMilliamperesFibrillationOSHAMSDSConfined spacesLockout and tagoutFire-retardant clothingScaffoldsEnergized circuitDisconnectedSafety OverviewAnticipatory SetGo over the eleven objectives of this unit and ask students what they already know about any of the objectives men-tioned. Promote classroom discussion on the subject of safety. Be careful to correct any mistakes.ANSWER TO REVIEW QUESTIONS1.To think before acting2.To prevent a current path directly through the heart.3.0.1–0.2 amperes4.When the heart quivers or vibrates and does not pump blood.5.It discharges a capacitor across the heart causing the heart of contract.6.The Secretary of Labor7.To ensure safe and healthy workplaces in the U.S.8.Material safety data sheet9.The electrician10.4 feet11.A current path to ground other than intended.12.5 mA13.Circuit breaker, receptacle, extension cord14.Class B fires involve fuels such as grease, combustible liquids or gases.15.NEC Section 250

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2Anticipatory SetTo prepare students for this unit, begin by stating the four objectives of the unit. Then, ask students what theyalready know about any of the four objectives. You may need to do a little prompting, such as asking what they re-member or know about atoms, positive/negative charges, things that conduct electricity, or things that do not con-duct electricity. Ask if anyone knows why you don’t use electrical tools in the rain, or why you do use rubber bootsto protect you from shock when working on a damp floor.1-1 Early History of ElectricityInstruct students to be prepared to define key terms in their notes as you proceed through the unit. Briefly discussthe two basic types of current. Follow up with a brief explanation of repulsion and attraction. Have some examplesfrom list A or B (p. 30 of text) to show these principles in action. Distinguish between negative and positive chargesas they relate to attraction and repulsion. Ask students if they know any other examples. Check for understanding byasking one or more students to explain the attraction/repulsion process.1-2 AtomsDefine an atom. Discuss the three principle parts of the atom, and discuss the role of each part as it relates to themake-up of the 90 natural elements and 23 artificial elements. Check for understanding before moving on.1-3 The Law of ChargesBegin discussion of the law of charges with a reminder of the principles of attraction/repulsion. This will help thestudents to immediately begin using previous learning as building blocks on which to attach new information. This is agood time to explain that everything in this text will build on principles learned, unit by unit. Discuss charges that attractand charges that repel. Using the PowerPoint®presentation, follow the outward-going and inward-going charges.Explain the two theories about why protons having the same charge do not break apart in the nucleus. Check for un-derstanding. Have students draw the proton-electron relationship and the proton-proton relationship in their notes.1-4 Structure of the AtomAsk students for to explain the similarities between how the planets orbit the sun in the solar system and the man-ner which electrons orbit the center of the atom. Point out that both the planets and electrons exist in exact specificorbits determined by their size (mass) and speed.UNIT 1Atomic StructureOUTLINE1-1Early History of Electricity1-2Atoms1-3The Law of Charges1-4Structure of the Atom1-5Electron Orbits1-6Valence Electrons1-7Electron Flow1-8Insulators1-9Semiconductors1-10Molecules1-11Methods of Producing Electricity1-12Electrical EffectsKEY TERMSAlternating current (AC)AtomAtomic numberAttractionBidirectionalConductorDirect current (DC)ElectronElectron orbitElementInsulatorsMatterMoleculesNegativeNeutronNucleusPositiveProtonRepulsionSemiconductorsUnidirectionalValence electrons

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31-5 Electron OrbitsThe section on electron orbits may call for a review of some basic mathematics.When discussing electron orbits, be sure that students understand how to determine the maximum number of elec-trons that can be in any given orbit. To check for understanding of the 2(N)2formula, write some arbitrary possibil-ities on the board or overhead: 2(5)2, 2(3)2, 2(8)2, and so on. Have students tell you how many electrons are in theorbit, and the number of the orbit, or shell: 50/5th orbit, 18/3rd orbit, 128/8th orbit, and so on.Stop here, and review the definitions of all key terms covered in the first five sections: direct current, alternating cur-rent, repulsion, attraction, atom, matter, element, electron, neutron, proton, quarks, nucleus, atomic number, oppositeand like charges, and gluon. Have students explain these various terms. Review how they are related to each other.1-6 Valence ElectronsExplain valence electrons and explain that the inner shells will have more electrons than the valence shell, as ex-plained with 2(N)2. Good examples of this are PowerPoint slides corresponding toFigures 1–15and1–16. Explainhow atoms with fewer valence electrons make better update conductors and why atoms with a higher number of va-lence electrons resist conductivity.1-7 Electron FlowDiscuss electron flow using the cue ball example. Ask students to give other examples (shuffle board, croquet, etc.).Be sure that students understand the directional flow of the energy from the impacting electron and how that energyis split by this directional flow, lessening the energy flow in each direction.1-8 InsulatorsReview what the maximum number of valence electrons is (8) and how this results in the creation of insulators.Have students give examples of insulators used in various professions (boots, gloves, etc.) or in household appliances(electrical cords).1-9 SemiconductorsExplain semiconductors and give examples of how they are used (in computers, for example).1-10 MoleculesDefine molecules, and have students distinguish between molecules and atoms. See if students can explain, usingwhat they have learned about electrons and valence shells, how two atoms might form a compound.1-11 Methods of Producing ElectricityGo over, one by one, each of the ways to produce electricity. Discuss the benefits of using one way over another,for a particular purpose. Point out terms the student should become familiar with, such aspiezo, Seebeck, photons, pho-tovoltaic, photoemissive, photoconductive, solar cells,andcad cells. Take some time to discuss the production of electricityfrom light, as it is so widely used.1-12 Electrical EffectsDiscuss how electricity can create some of the various effects, heat, light, pressure, magnetism, and chemical reac-tions that it is created from. Give examples of the various uses of electricity, in these ways. For example, if you have ac-cess to a crystal radio or earphone, it would be extremely beneficial for the student to see this process in action. Perhapsyou can copper plate something, or discuss the difference in buying gold plated jewelry versus solid gold jewelry. Per-haps a discussion of the way electrolysis is used would also be helpful. Having a variety of light bulbs, of differentwattages, might be a good way for students to explain how light is produced, and the results in heat watts and light watts.Unit Round UpReview all terms from the unit, including those terms covered in Sections 1-6 through 1-10: valence electrons,conductor, electron flow, insulators, semiconductors, and molecules. Review basic principles covered in the unit, andcheck for understanding by having students explain to you how these principles work. It is also a good idea for theinstructor to review the test from the’s Guide to assure that all necessary material was covered well enoughfor students to answer all test questions.

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4At NoSeqSymName11HHydrogen22HeHelium33LiLithium44BeBeryllium55BBoron66CCarbon77NNitrogen88OOxygen99FFluorine1010NeNeon1111NaSodium1212MgMagnesium1313AlAluminum1414SiSilicon1515PPhosphorous1616SSulfur1717ClChlorine1818ArArgon1919KPotassium2020CaCalcium2121ScScandium2222TiTitanium2323VVanadium2424CrChromium2525MnManganese2626FeIron2727CoCobalt2828NiNickel2929CuCopper3030ZnZinc3131GaGallium3232GeGermanium3333AsArsenic3434SeSelenium3535BrBromine3636KrKrypton3737RbRubidium3838SrStrontium3939YYttrium4040ZrZirconium4141NbNiobium4242MoMolybdenum43(1)TcTechnetium4443RuRuthenium4544RhRhodium4645PdPalladium4746AgSilver4847CdCadmium4948InIndium5049SnTin5150SbAntimony5251TeTellurium5352IIodine5453XeXenon5554CsCesium5655BaBarium5756LaLanthanum5857CeCerium5958PrPraseodymiumAt NoSeqSymName6059NdNeodymium61(2)PmPromethium6260SmSamarium6361EuEuropium6462GdGadolinium6563TbTerbium6664DyDysprosium6765HoHolmium6866ErErbium6967TmThulium7068YbYtterbium7169LuLutetium7260HfHafnium7371TaTantalum7472WTungsten7573ReRhenium7674OsOsmium7775IrIridium7876PtPlatinum7977AuGold8078HgMercury8179TlThallium8280PbLead8381BiBismuth8482PoPolonium8583AtAstatine8684RnRadon8785FrFracium8886RaRadium8987AcActinium9088ThThorium9189PaProactinium9290UUranium93(3)NpNeptunium94(4)PuPlutonium95(5)AmAmericium96(6)CmCurium97(7)BkBerkelium98(8)CfCalifornium99(9)EsEinsteinium100(10)FmFermium101(11)MdMendelevium102(12)NoNobelium103(13)LrLawrencium104(14)RfRutherfordium105(15)DbDubnium106(16)SgSeaborgium107(17)BhBhorium108(18)HsHassium109(19)MtMeitnerium110(20)UunUnunnilium111(21)UuuUnununium112(22)UubUnunbium114(23)UuqUnunquadiumSeq—sequence—plan number is natural element.Number in parentheses is artificial element.

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5UNIT 2Electrical Quantities and Ohm’s LawOUTLINE2-1The Coulomb2-2The Ampere2-3The Electron Flow Theory2-4The Conventional Current Flow Theory2-5Speed of Current2-6Basic Electric Circuits2-7The Volt2-8The Ohm2-9The Watt2-10Other Measures of Power2-11Ohm’s Law2-12Metric PrefixesKEY TERMSAmpere (A)British thermal unit (Btu)Complete pathConventional current flow theoryCoulomb (C)Electromotive force (EMF)Electron flow theoryGrounding conductorHorsepower (hp)ImpedanceJouleNeutral conductorOhm (Ω)Ohm’s lawPotential differencePowerResistanceVolt (V)Watt (W)Anticipatory SetGo over the eight objectives of this unit and ask students what they already know about any of the objectives men-tioned. Be careful to correct any mistakes. For example, a student may tell you that an amp is something that he plugshis guitar into. You might even hear that an ohm is a sound you make when meditating! A little humor here relaxesthe students and creates a classroom environment geared to active learning. Begin a question/answer session on thevarious types of measurements that students are already familiar and comfortable with. Tell them that this unit is sim-ply an explanation of a set of measurements for electricity.2-1 The CoulombExplain that the coulomb is a quantity measurement. A good visual aid is a 1- or 2-liter bottle of soda water. Showthe students that it is the amount of soda water in the bottle that makes the measurement of 2 liters an accurate one.This is what “quantity” measurement means. Using that same 2-liter bottle, let it represent 1 coulomb tossed into thePacific Ocean.As you define Coulomb’s law of electrostatic charges, write the equation on the board. Use two items to put intothe Q1and Q2positions. Also, inform students what a dielectric constant is and how dielectric breakdown can occur.2-2 The AmpereExplain that an ampere is simply another measurement unit: 1 coulomb per second. Explain the two types ofmeasurement involved in the ampere: quantity and time. Refer to the PowerPoint slide corresponding withFigure 2–1to show how an ampere of current flows through a wire when 1 coulomb flows past a point in 1 second. Illustrate thisby using the cue ball or another item that will roll or slide easily. Place a coin on top of a desk and roll or slide yourvisual aid past the coin. Explain that the moving object represents a coulomb, the coin is the point it passes, and anampere of electricity is what flowed through the unseen wire on the desktop. So, the ampere is the measurement ofthe amount (quantity) of electricity flowing through a circuit. Also, refer students toFigure 2–2in the text, makingthe water flow comparison.

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62-3 The Electron Flow TheoryBriefly state what the electron flow theory is, and draw the theory on the board showing this type of flow.Emphasize that this theory is the one that will be used throughout the text.2-4 The Conventional Current Flow TheoryExplain this theory carefully, making sure that students take note of the difference in flow: + to - versus - to + inthe two theories. Discuss why the conventional flow theory is preferred. Use the car battery example and check forunderstanding. Remember to double check for understanding on the direction that electronsalwaysflow, and makesure the students know that the electron theoryisthe one that will be used throughout this text.2-5 Speed of CurrentEstablish with students that a current is the flow of electrons through a conductive substance. Refer to the exam-ple with the table-tennis balls inFigure 2–6. Try to acquire a piece of 3/4-inch or 1-inch pipe and some table-tennisballs. Doing this visually in class will sink home the message of the nearly instantaneous effect of electrical impulses.Also, remind students to try to count how long it takes a bulb to light up once a switch has been flipped. Here is aflow of electrons, the current having been activated by flipping the switch, and the speed of that flow is so fast thatthe bulb lights up before our hand is off the switch!2-6 Basic Electric CircuitsExplain closed circuits and open circuits. Emphasize the loop quality of a closed circuit. Refer back to the lightswitch example to illustrate how a switch is used to open a circuit when not in use, and to close a circuit when it is inuse. Explain how short circuits occur, and why proper circuits and proper insulators must be used to prevent wiresforming unintended short circuits. Now, add to this the explanation on grounded circuits. Have a three-prong plugor adapter to show students during this explanation. Be sure to distinguish between the grounding conductor and theneutral conductor.2-7 The VoltDefine volt for the class and distinguish it from an ampere. An ampere is a quantity measurement of electricityflowing through a circuit, whereas a volt is the pressure, or electromotive force, that pushes those electrons througha wire. If you refer back to the pipe and the table-tennis balls, a volt is the ball that hits the last ball in line, forcingthe first ball in line out of the pipe.Explain the potential aspect of the volt and define a joule (J) for the class, letting them know that they will see thisword again in the discussion of watts (W). Check for understanding by having students explain that voltage pushescurrent through a wire but does not actually flow through the wire, as an ampere does. Students should realize thatvoltage is a potential force pushing electricity along a current waiting to be activated. As an example, note that thewall socket has voltage, or potential, but to release that force a circuit must be activated by plugging something intothat socket.2-8 The OhmDefine ohm for the class. Refer toFigure 2–12andFigure 2–13in the text, and use the text’s example of runningon the beach to explain resistance. To further illustrate resistance, use the comparison of weight lifting. The moreweight you try to lift, the more your body resists the weight. Your body does this to protect you. An ohm serves asimilar function in controlling the flow of electrons in an electric circuit. Just as your muscles would short-circuit onyou under too much pressure, the electric circuit will short out with a power overload.2-9 The WattDefine wattage and compare it to the ampere. Make the point that both of these are quantity measurements, butthe watt is the power flow resulting from the electric flow (amperes) times the force applied to that flow (volts).Wattage is not a flow of current; it is a resulting amount of power.

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7Explain the need for energy conversion to occur before true power (watts) can exist. The electrical energy flowingthrough a circuit must be converted into another type of energy. Use the example of a young but extremely activechild. The parent may enroll that child in several sports-related activities to convert wild or destructive energy intofocused and purposeful energy. With electricity, that conversion can be to heat energy or mechanical energy.2-10 Other Measures of PowerExplain the definition of horsepower (hp). A drawing, even a primitive one, will be helpful. Draw a horse, with arope hooked to a harness on the horse. Have the rope go up and through a pulley, and attach the rope to a weight.Change the poundage amount of the weight to work the formula several times. This visual aid will help students graspthe definition of horsepower. Then, show the equality of horsepower to watts.Define British thermal unit (Btu), and compare it to the calorie in the metric system. Discuss what a joule is again,and that 1 joule = 1 watt/second. Refer toFigure 2–17,and have students copy this conversion chart into the front oftheir notebooks for easy access, or make copies of this chart, and perhaps all conversion charts included in this text,and distribute to students.Have students work the sample problem, then add people (a few at a time, at an average weight of 160 lbs. each),and have students figure the amount of hp needed for each new weight. Continue with these examples until the classis comfortable with this formula. Then, practice with the Btu formula and use other examples, changing the high tem-perature desired and/or the amount of the water to be heated.2-11 Ohm’s LawGo over Ohm’s law carefully, and have students explain what it means. Students can get confused if they don’tbreak it down one section at a time. For clarification, go over each of the three formulas, making sure students un-derstand that the level of resistance is equal to the number of ohms.Next, show students how they can solve for R, I, or E, if they have the two components that make up the missingamount. For example, show students that if they know the I and R, they can find the E (E = I×R). If they need tofind I, they can divide R into E. If they need to find R, they divide I into E. Practice all three of these formulas sev-eral times until students are comfortable with them.A quick memory tool that your students can use here is the triangle:EIRStudents can see that I = E/R, that R = E/I, and that E = R×I. It is a handy reminder of the three formulas.Display the formula chart inFigure 2–20on the overhead. Explain how the chart can be used, based on the infor-mation they have. Do several practice problems using this “Dial-A-Formula” chart, covering the examples given inthe text.2-12 Metric PrefixesIf your students are like most Americans, just the mention of the metric system can cause them to break out in acold sweat. This lack of knowledge concerning the metric system can lead to learning blocks whenever the metricsystem is involved. As a teacher, you must help students overcome this anxiety. Explain that you are only concernedwith a very basic knowledge of the metric system, and either have students copy the chart fromFigure 2–24,or havea handout that they can put into their notebooks near the front for easy access. They also need to copy the chart fromFigure 2–25.Unit Round UpTake as much time as is necessary to review this unit. It is a vitally important unit. Students need to be able to workwith the various concepts and formulas comfortably and use them interchangeably. Go through the summary to-gether, and assign the review questions to double-check for complete understanding. Check these assignments beforemoving to the next unit to see if any reteaching needs to be done. Review all key terms from the unit.

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8ANSWERS TO PRACTICAL APPLICATIONS1.Yes the circuit is large enough. 20 A×0.80 = 16 A. 500 W×8 = 4000 W. 4000 W/277 V = 14.44 A.2.The first problem is that the circuit is too small to operate the furnace (15,000 W/240 V = 62.5 A). The cir-cuit breaker does not always trip because the heating strips come on in stages. The third stage may not alwaysturn on. The problem will have to be solved by connecting a larger circuit breaker and probably a largerconductor size to the furnace. The circuit breaker must be larger than 78.125 A (15,000 W/240 V = 62.5 A)(62.5 A×1.25 = 78.125 A).3.Three fans can be connected to a single 15-ampere circuit. Two circuits will be required. Since the loads arecontinuous duty, the circuit current is limited to 80% of the circuit rating or 12 amperes (15×0.80 = 12).Each fan contains four 60-watt lamps for a total of 240 watts. The current draw for the lamps is 2 amperes(240/120 = 2). The motor current of 1.8 amperes makes a total of 3.8 amperes per fan (2 + 1.8 = 3.8). Eachcircuit could supply power to 3.16 fans (12/3.8 = 3.16).4.Yes, the 20-ampere circuit can supply power to both the lamp and the motor. Continuous circuit current is16 amperes for a 20-ampere circuit (20×0.80). The 600-watt lamp has a current draw of 5 amperes(600/120) and the motor current is 8.5 amperes. Total circuit current is 13.5 amperes.UNIT 3Static ElectricityOUTLINE3-1Static Electricity3-2Charging an Object3-3The Electroscope3-4Static Electricity in Nature3-5Nuisance Static Charges3-6Useful Static ChargesKEY TERMSElectroscopeElectrostatic chargesLightningLightning arrestorLightning boltsLightning rodsNuisance static chargesPrecipitatorsSeleniumStaticThundercloudUseful static chargesAnticipatory SetUnit 3 is a very basic, simple unit. Go over the objectives and ask students to share experiences they have had in-volving static electricity. Have some visual aids on hand to help illustrate the principles of electrostatic charges. Theseaids might include a rubber rod, a piece of wool, a plastic comb, some tissues, an inflated balloon, and some picturesyou copied on a copy machine. When you make these copies, make them progressively darker so that you can showthe process in even more vivid detail.3-1 Static ElectricityAs you discuss the various uses of static electricity, and include the explanation of precipitators, ask students toname a household item that may use this process (an air-conditioning unit). Be sure that students understand whatstatic means, and that it is a charge, not a current. It is similar to voltage in that it is a charge waiting to be released,as a volt is potential force waiting for a current to push. Also, point out the electron theory in action here.Be sure that students realize that insulators hold electrons, and that is why electrostatic charges build on them.Make sure students understand that a lack of electrons means a majority of protons and, thus, a positive charge. Theinverse of this also needs to be explained.

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93-2 Charging an ObjectExplain that this is merely an extension of the principles discussed in the first section. Here, we use these princi-ples to electrostatically charge items by choice.Have students experiment with visual aids, building up static charges. The comb can be run through someone’sdry hair and then used to pick up pieces of the tissue. The balloon can be rubbed on someone’s dry hair (or on thewool) and then suspended on a wall.3-3 The ElectroscopeDescribe an electroscope and explain its function. If it is possible, have an electroscope in the classroom. Studentscould use the various things they used earlier and determine what type of charge the various items took on.3-4 Static Electricity in NatureDefine lightning as the result of static electricity, discuss why the flow of electricity sometimes moves from theclouds to the ground, and explain that it goes the other way at other times. Again, the electron theory explains thisupward or downward movement.Explain what lightning rods are, and make the distinction between them and lightning arrestors. Refer toFigures 3–9, 3–10,and3–11in the text to help illustrate those explanations.3-5 Nuisance Static ChargesBasically, just briefly touch on this, referring back to the things you did in Section 3-2. These principles have al-ready been discussed. However, ask your students to explain why the various types of products that can be put in thedryer with wet clothes (Bounce, Downy Dryer Sheets, Cling, etc.) prevent the static from building up in the clothes.Ask them why an aerosol spray product made for this purpose can eliminate static cling when sprayed directly on theclothing. Ask why some clothing items cling together, while others do not (e.g., rayon socks do, but denim jeans donot; pantyhose do, but heavy towels do not).3-6 Useful Static ChargesDiscuss the various useful ways in which static electricity is used. When explaining how the copy machine works,display your series of progressively darker copies. Have students explain how the copies became progressively darker(beyond the obvious answer of pushing the button to make them darker).Unit Round UpSummarize the unit, review all key terms, and double-check for understanding. If necessary, go back through anyprevious explanations, using the visual aids.UNIT 4MagnetismOUTLINE4-1The Earth Is a Magnet4-2Permanent Magnets4-3The Electron Theory of Magnetism4-4Magnetic Materials4-5Magnetic Lines of Force4-6Electromagnetics4-7Magnetic Measurement4-8Magnetic Polarity4-9Demagnetizing4-10Magnetic Devices

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10KEY TERMSAmpere-turnsDemagnetizedElectromagnetsElectron spin patternsFluxFlux densityLeft-hand ruleLines of fluxLodestonesMagnetic domainsMagnetic moleculesMagnetomotive force (mmf)Permanent magnetsPermeabilityReluctanceResidual magnetismSaturationAnticipatory SetThis is another unit in which students will greatly benefit from several visual aids. Gather magnets of various sizes,some cardboard (even several sheets of paper stacked together will work), some paper clips, and perhaps a model, oractual, electromagnet. Use PowerPoint presentationFigures 4–2, 4–5, 4–6, 4–7, 4–10, 4–11, 4–14, 4–15,and4–17.State the unit objectives.4-1 The Earth Is a MagnetGive the explanation of true geographic north versus magnetic north. Have students drawFigure 4–2into theirnotes, labeling the four poles, the polar axis, and magnetic flux lines. After they drawFigure 4–2into their notes, ex-plain why a compass points toward true magnetic north instead of to geographic north. Have students look at theirdrawing as you explain this.4-2 Permanent MagnetsDefine permanent magnets, and have some to show your students (even if they came off your refrigerator and havea phone number for ordering pizza on them, or a pig, or a cow, etc.). Be sure students write the definition of a per-manent magnet into their notes, as well as the basic law of magnetism given in this section.4-3 The Electron Theory of MagnetismExplain electron spin patterns and how they affect, or account for, the magnetic qualities or lack of magnetic qual-ities in an object. Refresh students’ memories by reminding them that the valence shell and, therefore, the valenceelectrons are at the outermost contact points of an atom. The valence shell is the outermost shell, or orbit, of an atom.Explain magnetic domains or magnetic molecules, and how these are formed by iron, nickel, and cobalt sharingelectrons in a way that does not cancel out their magnetic fields. Have students refer toFigures 4–5through4–7,anduse these PowerPoint slides.4-4 Magnetic MaterialsDiscuss the three classifications of magnetic materials. Explain what an alloy is, and why it makes better permanentmagnets. Perhaps students can figure it out for themselves, just in knowing what the alloy Alnico 5 is made of. Referthem to the Ferromagnetic materials list, and ask them to explain why Alnico 5 makes such a good permanent magnet.Discuss ceramic magnets and, if possible, show some examples to the class.4-5 Magnetic Lines of ForceExplain what flux is, and have students make note of its symbol in their notes. If you have the magnets and iron fil-ings, this is the time to use them to display flux lines in action. If you do not have these items, useFigures 4–10and4–11to illustrate this process. Make sure students understand that magnetic lines of flux never cross each other but repel eachother instead. Also, have students make note of another basic law of magnetism: like poles repel and unlike poles attract.4-6 ElectromagneticsExplain how a magnetic field is formed and how electric current is necessary to produce the magnetic field.Remind students that permanent magnets maintain their magnetism without electrical current, whereas electromag-nets usually do not.

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