1 Daily phenomena Basic Definitions 1 Electrostatics Next SlideDaily phenomena“Charge” plastic materials by frictionExperience of electric force and electric chargeRepulsive and attractive electric forceDifferent kinds of charge : positive (+) and negative (-)General Rule : like charges repel; unlike charges attract
2 Nature of charges Basic Definitions 2 Electrostatics Next SlideNature of chargesStructure of atoms and matterDiagramBalance of charge : no. of electrons = no. of protonsNeutral : no. of electrons = no. of protonsDiagramPositively charged : no. of electrons < no. of protonsNegatively charged : no. of electrons > no. of protonsCharging by changing the no. of electrons only
3 Nature of charges Basic Definitions 3 Electrostatics Next SlideNature of chargesUnit : Coulomb (C)Insulators (like plastics) : do not allow electrons to flow through them or escape easilyConductors (like metals) : allow electrons to flow through them or escape easilyCharging by frictionDiagramInduced chargeDiagram
4 Different ways of charging ElectrostaticsNext SlideDifferent ways of chargingCharging by extra high tension power (EHT) supplyPhotoCharging by Van de Graaff generatorPhotoCharging by sharingDiagramCharging by induction and separationDiagramCharging by induction and earthing processDiagram
5 Nature of electric field ElectrostaticsNext SlideNature of electric fieldPresence of electric field : experience of electric force by a small charge around a charged objectRepresentation of electric field : field linesElectric field pattern around a positive chargeDiagramElectric field pattern around a negative chargeDiagramVarious electric field patternsDiagramExperimental setup to demonstrate electric fieldsPhoto
6 Application of charges Applications 1ElectrostaticsNext SlideApplication of chargesAction of a pointDiagramLightning conductor and action of a pointDiagramElectrostatic precipitationPhotocopying
7 Electrostatic hazards Applications 2ElectrostaticsNext SlideElectrostatic hazardsSheets of paper stick together in industryWool, cotton and artificial fibres attract dustSparks produced in vehicles and planes
9 Back to Basic Definitions 2 Electrostatics Click Back to Matter is made up of tiny particles called atomsModel of an atom :nucleuselectron : negative (-) chargeproton : positive (+) chargeneutron : no chargeA proton has a positive charge and an electron has an equal negative charge while a neutron is uncharged
10 Back to Basic Definitions 2 Electrostatics Click Back to Assume that we have a rod which is made of atoms and each atom contains 2 protons, 2 neutrons and 2 electronsElectrically neutral (normal case)protonsneutronselectrons20000Positively chargedprotonsneutronselectrons2000018000Negatively chargedprotonsneutronselectrons2000023000
11 Back to Basic Definitions 3 Electrostatics Click Back to When a plastic rod is rubbed with a dry cloth, we have either one of the following cases.flow of electronsflow of electronsPlastic rod : +ve chargedCloth : -ve chargedPlastic rod : -ve chargedCloth : +ve charged
12 Back to Basic Definitions 3 Electrostatics Click Back to A charged (either +ve or -ve) rod can attract a piece of aluminium foil which is neutral initially.flow ofelectronsAluminiumflowSince the electrons are attracted towards the upper end, the upper part becomes -ve while the lower part becomes +ve.large attractive forceSince smaller separation means larger force, the attractive force is always larger than the repulsive force.small repulsive force
13 Back to Ways of charging Electrostatics Click Back to Extra high tension (EHT) power supply
14 Back to Ways of charging Electrostatics Click Back to Van de Graaff generator
15 Ways of charging Electrostatics Next Slide Consider two metal spheres which are supported by insulating stands as shown.One of the sphere is negatively charged while the other one is uncharged.Insulating standsNegativelycharged sphereUnchargedsphere
16 Ways of charging Electrostatics Next Slide They are brought into contact with each other.Some of the electrons flow from the charged sphere to uncharged sphere.flow of electronsBoth objects are then negatively charged.
17 Back to Ways of charging Electrostatics Click Back to Both spheres are then separated and negatively charged.This is called charging by sharing.
18 Ways of charging Electrostatics Next Slide Consider two metal spheres which are supported by insulating stands as shown.Both spheres are neutral and they are in contact with each other as shown.Insulating standsUnchargedspheres
19 Ways of charging Electrostatics Next Slide A positively charged rod is brought near one of the sphere.Induced charge appears as electrons flow from one sphere to another.Insulating standsflow of electrons
20 Ways of charging Electrostatics Next Slide The spheres are separated without removing the rod.Insulating stands
21 Back to Ways of charging Electrostatics Click Back to Then we remove the rod. One sphere is negatively charged while the other one is equally positive charged.No loss of charge from the charged rodThis is the method of charging by induction and separation.Insulating stands
22 Ways of charging Electrostatics Next Slide We have a uncharged conducting sphere supported by insulating stand.A positively charged rod is brought near the sphere.Induced charge appears in the sphere.Insulating standsflow of electrons
23 Ways of charging Electrostatics Next Slide Touch the sphere with your finger or collect the sphere to the earth with a conducting wire without removing the rod.Electrons flow from the earth to the sphere and neutralize the +ve charge on the other side in the sphere.Insulating standsflow of electronsearthingprocess
24 Ways of charging Electrostatics Next Slide Remove the finger or the wire without removing the rod.Insulating stands
25 Back to Ways of charging Electrostatics Click Back to Remove the rod and we get a negatively charged sphere.No loss of charge in the rod is involved.This is the method of charging by induction and earthing process.Insulating stands
26 Back to Electric field Electrostatics Click Back to The electric field pattern around a positive charge is shown.The arrows and the lines represent the direction of force acting on a very small testing charge placed at that point.
27 Back to Electric field Electrostatics Click Back to The electric field pattern around a negative charge is shown.The arrows and the lines represent the direction of force acting on a very small testing charge placed at that point.
28 Electric field Electrostatics Next Slide Various patterns are shown in the following figures:
31 Back toElectric fieldElectrostaticsClick Back to
32 Applications 1 Electrostatics Next Slide Action of a point : The charge has a tendency to concentrate on the sharp points of a conductor. Around these points, the electric field is so strong that the air molecules are ionized.
33 Back to Applications 1 Electrostatics Click Back to Let’s take a negatively charged object with a sharp end as an example. Positive ions are attracted towards the point while negative ions are repelled.Positive ions remove some electrons from the object and become neutral again. The charge on the object is reduced.The negative ions are repelled and move away from the point. The stream of ion flow is called electric wind.electric wind
34 Back to Applications 1 Electrostatics Click Back to Lightning conductor is a metal rod with sharp ends and installed as shown in the following figure.electric windLightning conductor provides a route for electrons (lightning) to pass into the ground.Electric wind reduces the charge on the cloud and the induced charge on the roof.