Chapter 32Chapter 32

ElectrostaticsElectrostatics

ELECTRICITY is ELECTRICITY is EVERYWHEREEVERYWHERE

LighteningLighteningStatic electricity(when you Static electricity(when you

“shock” someone by “shock” someone by touching them)touching them)

Atoms are held together in Atoms are held together in moleculesmolecules

ElectrostaticsElectrostaticsElectricity(electric Electricity(electric

charges) at restcharges) at rest“…“…static's” means static's” means

something is at restsomething is at rest

32.1 Electrical forces and 32.1 Electrical forces and chargescharges

Electrical forcesElectrical forces-a force -a force one electric charge exerts one electric charge exerts on anotheron another

charges may be positive charges may be positive (+) or negative(-)(+) or negative(-)

32.1 Electrical Forces 32.1 Electrical Forces and Chargesand ChargesIf both are the same they If both are the same they

repel each otherrepel each otherIf charges are different, If charges are different,

they are attracted to each they are attracted to each other.other.

32.1 Electrical Forces 32.1 Electrical Forces and Chargesand ChargesCharge-the property to Charge-the property to

which the mutual repulsion which the mutual repulsion or mutual attraction of or mutual attraction of electrons and protons is electrons and protons is attributed attributed

Electrons are –Electrons are –Protons are +Protons are +

32.2 Conservation of 32.2 Conservation of ChargeCharge

““An object that has an An object that has an unequal number of unequal number of electrons and protons electrons and protons is electrically is electrically charged…charged…

32.2 Conservation of 32.2 Conservation of ChargeCharge

……if it has more if it has more electrons than protons, electrons than protons, the object is negatively the object is negatively charged…charged…

32.2 Conservation of 32.2 Conservation of ChargeCharge

……if it has fewer if it has fewer electrons than electrons than protons , it is positively protons , it is positively charged.”charged.”

32.3 Coulomb’s Law 32.3 Coulomb’s Law Charles Coulomb (1736-Charles Coulomb (1736-

1806)1806)Coulomb-SI unit for chargeCoulomb-SI unit for chargeabbreviation:Cabbreviation:CC=charge of electrons(6.25 C=charge of electrons(6.25

billion billion electrons)billion billion electrons)equivalent to the charge that equivalent to the charge that

runs through a 100-watt runs through a 100-watt bulbbulb

32.3 Coulomb’s law32.3 Coulomb’s law

““for charged particles or for charged particles or objects that are small objects that are small compared to the distance compared to the distance between them…between them…

32.3 Coulomb’s law32.3 Coulomb’s law

……(1) the force between (1) the force between the charges varies the charges varies directly as the product of directly as the product of the charges and(2) the charges and(2) inversely as the square of inversely as the square of the distance between the distance between them.”them.”

32.3 Coulomb’s law32.3 Coulomb’s law

F= k x F= k x qq11 x q x q22

dd22

F= the force between chargesF= the force between charges

qq11 & q & q22=quantity of charge=quantity of charge

dd22=distance between particles=distance between particles k=9,000,000,000(N x mk=9,000,000,000(N x m22)/C)/C22

32.4 Conductors and 32.4 Conductors and InsulatorsInsulators

ConductorConductor- a material usually a - a material usually a metal, through which an metal, through which an electric charge can flow.electric charge can flow.

-Electrons are not anchored on -Electrons are not anchored on the nucleus, but are allowed to the nucleus, but are allowed to roam in the materialroam in the material

32.4 Conductors and 32.4 Conductors and InsulatorsInsulators

InsulatorsInsulators- a material that is - a material that is poor conductor of electricitypoor conductor of electricity

-the electrons are anchored to -the electrons are anchored to the nucleus and not free to the nucleus and not free to roamroam

32.4 Conductors and 32.4 Conductors and InsulatorsInsulatorsSemiconductorsSemiconductors- -

material that can be material that can be made to behave as made to behave as either a conductor or either a conductor or an insulator of an insulator of electricityelectricity

32.4 Conductors and 32.4 Conductors and InsulatorsInsulators

SuperconductorSuperconductor- - materials that have materials that have zero resistance to the zero resistance to the flow of chargeflow of charge

-(infinite conductivity)-(infinite conductivity)

32.5 Charging by friction 32.5 Charging by friction and Contact (OH)and Contact (OH)

--ex: static electricity ex: static electricity after you rub your feet after you rub your feet against the flooragainst the floor

32.6 Charging by 32.6 Charging by induction induction

(OH 76, 77)(OH 76, 77)

InducedInduced-term applied to -term applied to electric charge that has electric charge that has been redistributed on an been redistributed on an object because of a object because of a charged object nearbycharged object nearby

32.6 Charging by 32.6 Charging by InductionInduction

1.1. Induction-Induction-the charging of the charging of an object without direct an object without direct contactcontact

aka:electromagnetic aka:electromagnetic inductioninduction

32.7 Charge Polarization32.7 Charge PolarizationElectrically polarizedElectrically polarized--term applied to an atom term applied to an atom or molecule in which or molecule in which charges are aligned so charges are aligned so that one side is slightly that one side is slightly more positive or more positive or negative than the negative than the opposite sideopposite side

32.7 Charge Polarization32.7 Charge Polarization

--Occurs in insulators Occurs in insulators that are in the that are in the presence of a charged presence of a charged objectobject