Electrostatics Chapter 23Most classes will begin with a slide similar to the following.What’s HappeningProbable First Observation ElectricityIdiot!A Quick ExperimentExperimental ProcedureAllowable Predictions (Use your clicker if you have one.)Experiment #1Experiment #2The charges on the two rods are ..If you rubbed the rods longer and/or harder, do you think the effect that you see would beIf the two rods are brought closer together, the force acting between them will get …Definition of sortsExperiment #3Experiment #4What’s Going On?We call these two types of chargeExample - TapeSlide 20An ExampleEffect of ChargeWe have also observed that there must be TWO kinds of charge.Old Ben screwed up more than once!!From whence this charge???MaterialsExperiment #5What about a charged rod and a piece of wood??Ways to charge an objectNeutral Object - POLARIZATIONInductionPolarizeGroundRemove GroundPositive !Slide 36Same as before: PolarizationWhat happens when two surfaces touch or rub?Slide 39So far we have found?Forces Between ChargesCoulomb’s Law – Force between chargesRememberCoulomb’s LawSlide 45Slide 46The Electric FieldFieldsExample – Gravitational Field.The Gravitational Field That We Live In.Slide 51This is WARNothing Happens! The Green thing is a Force Field!Side ViewProperties of a FORCE FIELDMysterious ForceElectric FieldTwo ChargesDoing itGeneral-Force  FieldSlide 62Two Charges What is the Electric Field at Point P?The two S’sWhat is the electric field at the center of the square array?Kinds of continuously distributed chargesContinuous Charge DistributionymmetryLet’s Do it Real TimeThe mathA Harder ProblemSlide 72Completing the MathDare we project this??The GeometrySlide 76Final ResultLook at the “Field Lines”What did we learn in this chapter??What else did we learn in this chapter?Slide 81The SphereSummaryTo be remembered …Electrostatics Chapter 23Most classes will begin with a slide similar to the following.What’s Happening•Clicker use will start on Friday (maybe). We will use them today informally.•There will NOTNOT be a quiz this week.•There WILLWILL be a quiz a week from Friday.•WebAssigns should be active shortly. Keep an eye out for it.•It might be already there !!!Probable First Observation ElectricityElectricityIdiot!If lightening had actually traveled down the kite string, old Ben Franklin would have been toast!Probably never happened, but good story!A Quick ExperimentExperimental ProcedurePivotThe sequence of Experiments1. Identify the two rods2. Treat each rod3. Bring one rod near to the other4. PREDICT WHAT WILL HAPPEN5. VOTE ON POSSIBILITIES6. Observe what happens7. Did you learn anything? What?Allowable Predictions(Use your clicker if you have one.)A. Rods will attract each otherB. Rods will repel each otherC. Nothing will happenD. Something not listed above will happenExperiment #1PivotmotionRubber rodRubber rodA. Rods will attract each otherB. Rods will repel each otherC. Nothing will happenD. Something not listed above will happenExperiment #2PivotRubber rubbed withskin of dead rabbitRubber rubbed withskin of dead rabbitA. Rods will attract each otherB. Rods will repel each otherC. Nothing will happenD. Something not listed above will happenThe charges on the two rods are ..A. Since we treated both rods in the same way, they should be of the same typeB. ……. different typesC. I have no idea what you are asking for.D. Leave me alone … I’m napping!If you rubbed the rods longer and/or harder, do you think the effect that you see would beA. StrongerB. WeakerC. The sameIf the two rods are brought closer together, the force acting between them will get …A. StrongerB. WeakerC. The sameDefinition of sortsWe DEFINE the “stuff” that we put on the rods by the rubbing process as CHARGE.We will try to understand what charge is and how it behaves.We add to the properties of materials:MassChargeChargeExperiment #3PivotGlass rubbed with woolA. Rods will attract each otherB. Rods will repel each otherC. Nothing will happenD. Something not listed above will happenGlass rubbed with woolExperiment #4Pivot1. Rods will attract each other2. Rods will repel each other3. Nothing will happen4. Something not listed above will happenGlass rubbed with woolRubber rubbed withskin of dead rabbitWhat’s Going On?All of these effects involve r ubbing two surfaces together.Or pulling two surfaces apart.Something has “happened “to each of these objects.These objects have a new PROPERTYOther properties are mass, colorWe call this NEW PROPERTY .………. ………CHARGE.There seems to be two types of charge.We call these two types of chargePositiveNegativeAn object without either a (+) or (-) charge is referred to as being NEUTRAL.NEUTRAL.Example - TapeSeparationAn ExampleEffect of ChargeWe have also observed that there must be TWO kinds of charge.Call these two typespositive (+)negative(-)We “define” the charge that winds up on the rubber rod when rubbed by the dead cat to be NEGATIVE.The charge on the glass rod or the dead cat is consequently defined as POSITIVE.Old Ben screwed up more than once!!++++++++++-------------+++---++---+-++-From whence this charge???-+Easily RemovedMaterialsTwo kinds of materials:InsulatorsElectrons and Protons are tightly bound to their positions. Hard to move them around.ConductorsElectrons are easily removed and moved around. Electrons are said to be MOBILE charges.There are other kinds of materials that we will not discuss: semiconductors, semi-metalsPivotExperiment #5Rubber rubbed withskin of dead rabbitMetal RodA. Rods will attract each otherB. Rods will repel each otherC. Nothing will happenD. Something not listed above will happenWhat about a charged rod and a piece of wood??A. Rods will attract each otherB. Rods will repel each otherC. Nothing will happenD. Something not listed above will happenWays to charge an objectRubbing or bond breaking (same thing)TransferDirect transferPolarizationInductionNeutral Object - POLARIZATIONPositive charge attracts negative charges.Rod becomes “polarized.Negative end is closer to positive chargeDistance effect causes attraction.InductionPolarizeGroundRemove GroundPositive !Balloon PhysicsSame as before: PolarizationWhat happens when two surfaces touch or rub? Bonding!Bonding!The Triboelectric SeriesNo! No!When two of the following materials are rubbed together under ordinary