Introduction15.1 Properties of Electric Charges - Discovery15.1 Properties of Electric ChargesNature of Electrical Charge15.1 Properties of Electric ChargesQuantization15.2 Insulators and Conductors –Material classificationMini-quiz:15.2 Insulators and Conductors – Charging by Conduction.15.2 Insulators and Conductors – Earth/Ground.15.2 Insulators and Conductors – Charging by Induction.15.2 Insulators and Conductors – Charging by Induction.15.2 Insulators and Conductors – Polarization.Mini-quizExplain why it is not possible to determine whether the object is negatively charged or neutral.What additional experiment is needed to reveal the electrical charge state of the object?15.3 Coulomb’s Law - Observation15.3 Coulomb’s Law – Mathematical FormulationExample15.3 Coulomb’s Law – RemarksMini-QuizExample: Electrical ForceQuestion:The electron and proton of a hydrogen atom are separated (on the average) by a distance of about 5.3x10-11 m. Find tSuperposition PrincipleExample: Using the Superposition PrincipleConsider three point charges at the corners of a triangle, as shown below. Find the resultant force on q3.119/3/20039/3/2003General Physics (PHY 2140)IntroductionIntroduction¾ Syllabus and teaching strategy¾ Electricity and Magnetism• Properties of electric charges• Insulators and conductors• Coulomb’s lawLecture 1. Chapter 15229/3/20039/3/2003Syllabus and teaching strategyLecturer: Prof. Alexey A. Petrov, Room 260 Physics Building, Phone: 313-577-2739, or 313-577-2720 (for messages)e-mail: [email protected], Web: http://www.physics.wayne.edu/~apetrov/Office Hours: MWF 10:40 AM -11:35 AM, General Lectures, Room 150Tuesday 1:00-2:00 PM, on main campus, Physics Building, Room 260, or by appointment.Grading: Reading Quizzes (bonus) 5%Quiz section performance/Homework 10%Best Hour Exam 25%Second Best Hour Exam 25%Final 40%Reading Quizzes:It is important for you to come to class prepared!BONUS POINTS: Reading SummariesHomework and QUIZ Sessions:The quiz sessions meet once a week; 5 quizzes will count towards your grade.BONUS POINTS: will be assigned by your quiz instructor.Hour Exams and Final Exam:There will be THREE (3) Hour Exams and one Final Exam.Additional BONUS POINTS will be given out for class activity.Online Content: Lecture Online will be made available to you as a supplemental reference.339/3/20039/3/2003IntroductionIntroductionKnowledge of electricity dates back to Greek antiquity Knowledge of electricity dates back to Greek antiquity (700 BC).(700 BC).Began with the realization that amber (fossil) when Began with the realization that amber (fossil) when rubbed with wool, attracts small objects.rubbed with wool, attracts small objects.This phenomenon is not restricted to amber/wool but may This phenomenon is not restricted to amber/wool but may occur whenever two nonoccur whenever two non--conducting substances are conducting substances are rubbed together.rubbed together.449/3/20039/3/200315.1 Properties of Electric Charges 15.1 Properties of Electric Charges --DiscoveryDiscoveryObservation of “Static Electricity”Observation of “Static Electricity”A comb passed though hair attracts small pieces of paper.A comb passed though hair attracts small pieces of paper.An inflated balloon rubbed with wool.An inflated balloon rubbed with wool.“Electrically charged”“Electrically charged”Rub shoes against carpet/car seat to charge your body.Rub shoes against carpet/car seat to charge your body.Remove this charge by touching another person/a piece of Remove this charge by touching another person/a piece of metal.metal.Two kinds of chargesTwo kinds of chargesNamed by Benjamin Franklin (1706Named by Benjamin Franklin (1706--1790) as 1790) as positivepositiveand and negativenegative..Like charges repel one another and unlike charges Like charges repel one another and unlike charges attract one anotherattract one another..559/3/20039/3/200315.1 Properties of Electric Charges15.1 Properties of Electric ChargesNature of Electrical ChargeNature of Electrical ChargeOrigin of charge is at the atomic level.Origin of charge is at the atomic level.Nucleus : “robust”, Nucleus : “robust”, positivepositive..Electrons : mobile, Electrons : mobile, negativenegative..Usual state of the atom is Usual state of the atom is neutralneutral..Charge has natural tendency to be transferred between Charge has natural tendency to be transferred between unlike materials.unlike materials.Electric charge is however always Electric charge is however always conservedconservedin the in the process.process.Charge is Charge is not creatednot created..Usually, Usually, negative chargenegative chargeis transferred from one object to the is transferred from one object to the other.other.669/3/20039/3/200315.1 Properties of Electric Charges15.1 Properties of Electric ChargesQuantizationQuantizationRobert Robert MillikanMillikanfound, in 1909, that charged objects may only have found, in 1909, that charged objects may only have an integer multiple of a fundamental unit of charge.an integer multiple of a fundamental unit of charge.Charge is Charge is quantizedquantized..An object may have a charge An object may have a charge ±±e, or e, or ±±2e, or 2e, or ±±3e, etc but not say 3e, etc but not say ±±1.5e.1.5e.Proton has a charge Proton has a charge +1e+1e..Electron has a charge Electron has a charge ––1e1e..Some particles such a Some particles such a neutronneutronhave no (zero) charge.have no (zero) charge.A neutral atom has as many positive and negative charges.A neutral atom has as many positive and negative charges.UnitsUnitsIn SI, electrical charge is measured in coulomb ( C).In SI, electrical charge is measured in coulomb ( C).The value of |The value of |e| = 1.602 19 x 10e| = 1.602 19 x 10--1919CC..779/3/20039/3/200315.2 Insulators and Conductors 15.2 Insulators and Conductors ––Material Material classificationclassificationMaterials/substances may be classified according to their capaciMaterials/substances may be classified according to their capacity to ty to carry or carry or conductconductelectric charge electric charge ConductorsConductorsare material in which electric charges move freely.are material in which electric charges move freely.Insulator Insulator are materials in which electrical charge do not move freely.are