Chapter 23Electricity and Magnetism, Some HistoryElectricity and Magnetism, Some History, 2Electricity and Magnetism, Some History, 3Electricity and Magnetism, Some History, 4Electric ChargesElectric Charges, 2Electric Charges, 3More About Electric ChargesConservation of Electric ChargesQuantization of Electric ChargesConductorsInsulatorsSemiconductorsCharging by InductionCharging by Induction, 2Charging by Induction, 3Charging by Induction, 4Charging by Induction, 5Charge Rearrangement in InsulatorsCharles CoulombCoulomb’s LawPoint ChargeCoulomb’s Law, 2Coulomb’s Law, 3Coulomb’s Law, EquationCoulomb's Law, NotesParticle SummaryVector Nature of Electric ForcesVector Nature of Electrical Forces, 2Vector Nature of Electrical Forces, 3A Final Note about DirectionsThe Superposition PrincipleSuperposition Principle, ExampleZero Resultant Force, ExampleElectrical Force with Other Forces, ExampleElectrical Force with Other Forces, Example cont.Electric Field – IntroductionElectric Field – DefinitionElectric Field – Definition, contElectric Field, NotesElectric Field Notes, FinalRelationship Between F and EElectric Field, Vector FormMore About Electric Field DirectionSuperposition with Electric FieldsSuperposition ExampleElectric Field – Continuous Charge DistributionElectric Field – Continuous Charge Distribution, contElectric Field – Continuous Charge Distribution, equationsCharge DensitiesAmount of Charge in a Small VolumeProblem-Solving StrategyProblem-Solving Strategy, contProblem Solving Hints, finalExample – Charged DiskElectric Field LinesElectric Field Lines, GeneralElectric Field Lines, Positive Point ChargeElectric Field Lines, Negative Point ChargeElectric Field Lines – DipoleElectric Field Lines – Like ChargesElectric Field Lines, Unequal ChargesElectric Field Lines – Rules for DrawingMotion of Charged ParticlesMotion of Particles, contElectron in a Uniform Field, ExampleChapter 23Electric FieldsElectricity and Magnetism, Some HistoryMany applicationsMacroscopic and microscopicChineseDocuments suggest that magnetism was observed as early as 2000 BCGreeksElectrical and magnetic phenomena as early as 700 BCExperiments with amber and magnetiteElectricity and Magnetism, Some History, 21600William Gilbert showed electrification effects were not confined to just amberThe electrification effects were a general phenomena1785Charles Coulomb confirmed inverse square law form for electric forcesElectricity and Magnetism, Some History, 31819Hans Oersted found a compass needle deflected when near a wire carrying an electric current1831Michael Faraday and Joseph Henry showed that when a wire is moved near a magnet, an electric current is produced in the wireElectricity and Magnetism, Some History, 41873James Clerk Maxwell used observations and other experimental facts as a basis for formulating the laws of electromagnetismUnified electricity and magnetism1888Heinrich Hertz verified Maxwell’s predictionsHe produced electromagnetic wavesElectric ChargesThere are two kinds of electric chargesCalled positive and negativeNegative charges are the type possessed by electronsPositive charges are the type possessed by protonsCharges of the same sign repel one another and charges with opposite signs attract one anotherElectric Charges, 2The rubber rod is negatively chargedThe glass rod is positively chargedThe two rods will attractElectric Charges, 3The rubber rod is negatively chargedThe second rubber rod is also negatively chargedThe two rods will repelMore About Electric ChargesElectric charge is always conserved in an isolated systemFor example, charge is not created in the process of rubbing two objects togetherThe electrification is due to a transfer of charge from one object to anotherConservation of Electric ChargesA glass rod is rubbed with silkElectrons are transferred from the glass to the silkEach electron adds a negative charge to the silkAn equal positive charge is left on the rodQuantization of Electric ChargesThe electric charge, q, is said to be quantizedq is the standard symbol used for charge as a variableElectric charge exists as discrete packetsq = NeN is an integere is the fundamental unit of charge|e| = 1.6 x 10-19 CElectron: q = -eProton: q = +eConductorsElectrical conductors are materials in which some of the electrons are free electrons Free electrons are not bound to the atomsThese electrons can move relatively freely through the materialExamples of good conductors include copper, aluminum and silverWhen a good conductor is charged in a small region, the charge readily distributes itself over the entire surface of the materialInsulatorsElectrical insulators are materials in which all of the electrons are bound to atoms These electrons can not move relatively freely through the materialExamples of good insulators include glass, rubber and woodWhen a good insulator is charged in a small region, the charge is unable to move to other regions of the materialSemiconductorsThe electrical properties of semiconductors are somewhere between those of insulators and conductorsExamples of semiconductor materials include silicon and germaniumCharging by InductionCharging by induction requires no contact with the object inducing the chargeAssume we start with a neutral metallic sphere The sphere has the same number of positive and negative chargesCharging by Induction, 2A charged rubber rod is placed near the sphereIt does not touch the sphereThe electrons in the neutral sphere are redistributedCharging by Induction, 3The sphere is groundedSome electrons can leave the sphere through the ground wireCharging by Induction, 4The ground wire is removedThere will now be more positive chargesThe charges are not uniformly distributedThe positive charge has been induced in the sphereCharging by Induction, 5The rod is removedThe electrons remaining on the sphere redistribute themselvesThere is still a net positive charge on the sphereThe charge is now uniformly distributedCharge Rearrangement in InsulatorsA process similar to induction can take place in insulatorsThe charges within the molecules of the material are rearrangedCharles Coulomb1736 – 1806French physicistMajor contributions were in areas of electrostatics
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