# Electricity  The Electric Charge  The Electron  Insulators and Conductors  The Gold-Leaf Electroscope  Redistribution of Charge  Charging by Induction.

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• ElectricityThe Electric ChargeThe ElectronInsulators and ConductorsThe Gold-Leaf ElectroscopeRedistribution of ChargeCharging by InductionCoulombs Law of Electric Force

• Electricity

• ObjectivesDefine the nature of electric charge, and describe how objects can obtain a negative or positive chargeDistinguish between insulators, conductors, and semi-conductorsExplain how the gold-leaf electroscope can be used to determine a chargeState and apply Coulombs Law

• ElectrostaticsStatic electricityStationary electricity in the form of a electric charge at restSymbol for charge is q or QUnit of chargeCoulombSymbol for coulomb is C

• Elementary ChargeSmallest unit of chargeCharge is quantized

Atoms contain elementary chargesElectron (-e) = -1.6 x 10-19 CProton (+e) = 1.6 x 10-19 CNeutron (0) = no charge

• The Electric ChargeNeutral objectsNumber of negative charges equals the number of positive chargesCharge is balanced (equilibrium)Charged objectsCharge is transferred from one object to anotherCharge is separated within an object

• The Electric ChargeFirst Law of Electrostatics: Like charges repel and unlike charges attract.A force of repulsion exists between two substances that are electrified in the same way.

• The ElectronAn object that has an excess of electrons is negatively charged.An object that has a deficiency of electrons is positively charged.

• Insulators and ConductorsA conductor is a material through which charges can be easily transferred.Such as metals, that allow charges to move about freelyCharges spread out over the surfaceAn insulator is a material that resists the transfer of charge.Materials through which charges will not move easilyCharges stay where they are placedA semiconductor is a material that transfers charges better than an insulator but not as well as a conductor.

• Charging by ConductionCharging a neutral object by touching it with a charged bodyCharges are transferred to the objectCharges spread over all metal surfaces

• Charging by InductionA charged body is brought near another object without touching itCharges are separated in the objectLike charges within the object are forced to move away from a charged body to another part of the objectOROpposite charges within the object are forced to move toward a charged body leaving like charges in another part of the object

• Charging by InductionDipole moment of water molecule

Water bends toward positive charge

• Charging by InductionDipole moment of water molecule

Water bends toward negative charge

• The Gold-Leaf Electroscope

• Redistribution of ChargeWhen a charged rod is brought close to an uncharged pith ball there is an initial attraction.

No charge is gained or lost during this process--the charge on the neutral body is simply redistributed.

• Charging by InductionCharging by induction: The redistribution of charge due to the presence of a nearby charged object.Charging by induction can be accomplished without any loss of charge from the charging body.

• Coulombs LawCoulombs LawThe force of attraction or repulsion between two point charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.One coulomb is the charge transferred through any cross-section of a conductor in one second by a constant current of one ampere.1 C = 6.25 x 1018 electronsk = 8.99 x 109 Nm2/C2

• Summary of New Termselectrostaticschargingelectronnegative chargepositive chargeioninduced chargeconductorinsulatorsemiconductorCoulombs lawcoulombmicrocoulombelectroscope

• ExampleWhat is the electrical force on A?