2What is Static Electricity The buildup of electrical charges in one place.Static = charge does not move or flow(usually a temporary condition).Can be detected by an electroscope.
3Examples of static electricity: Rubbing a balloon on your hairWalking across carpetClothes tumbling in dryerWhat do these have in common?Friction!!!!
4Creating Static Charges Static charges result when some charges are transferred from one object to another by frictionWhich charges are easily removed?Recall structure of the atom.
5Recall from ChemistryElectrons (-) are on the outside of the atom so they can be easily removed, while protons (+) are held firmly in the nucleusProtons & NeutronsElectrons
6Two Types of ChargeElectrons can be transferred by friction, but protons cannotTransferring protons would create a new element!LOSING electrons gives an object a POSITIVE chargeGAINING electrons gives an object a NEGATIVE chargeNOTE: When one object loses, another must gain - electrons can’t be created or destroyed
7BEFORECombing transfers electrons from the hair to the comb by friction, resulting in a negative charge on the comb and a positive charge on the hair.AFTER
8Induced chargeCharged and neutral objects (not touching) are attracted because electrons move in the neutral object.Electrons move toward a +ve charged object and away from a –ve charged one.This is called “induced charge”
9Conduction Conduction = direct transfer of charge Eg: walk across carpet and touch a doorknob shocking!Electrons are stripped from the carpet and you gain a net –ve chargeWhen you touch the doorknob, electrons jump onto it electrical discharge
11Attract Repel Neither Place an “X” in the appropriate box: +ve and -ve +ve and neutral+ve and +ve-ve and neutral-ve and –veNeutral and neutral
12Attract Repel Neither X Place an “X” in the appropriate box: +ve and -veX+ve and neutral+ve and +ve-ve and neutral-ve and –veNeutral and neutral
13Rules of static electricity Objects with like charges repel, but objects with unlike charges attractCharged objects attract neutral objects
14Does friction always create static charge? Different materials have different strength of attraction for electronsIf two objects of the same material are rubbed, no static charge forms(equal number of electrons transfer each way)
15If two different objects are rubbed, they have different attractions to the e- The stronger one will take e- away from weaker one and static charges build up
16Uses of static electricity Trapping particles in smokestacks of factoriesApplying grit to sandpaperSpray painting mesh (e.g. chain link fence)Powder coating
17The leaves are repelled by the like charge upon them.
187.2 Electric Force--Summary Force is a push or pull - electric force can do both, without touching the object - it is an action-at-a-distance force.Laws of Static ChargeLike charges repelOpposite charges attractNeutral objects are attracted to charged objectsSee pages
19Charging Objects Charging By Conduction Charging By Induction Charging through direct contactExtra electrons will move to a location where there is less of themCharging By InductionBringing a charged object nearby a neutral object will cause charge movement and separation in the in the neutral object(like charges repel!)See pages