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14
PartI
2.Ifenoughchargeisbuiltuponthesurfaceofanobject,thecharge
canflowthroughtheairandcauseanelectricarc.
3.Wecanearthanobjecttocauseanelectricarc.
4.Ifachargedobjectisputnearanunchargedobject,itwillcause
positivechargeontheunchargedobject.
5.Weinduceelectricchargebytouchinganobjectwithanelectrically
chargedobject.
6.TheunitofchargeisColumb.
Youhavecertainlynoticedthatyourcomputermonitorgetsdustyquicker
thanotherfurnitureinyourroom.Thisisbecauseelectricchargebuildsuponit
andattractstheparticlesofdust.Butwhyisunchargeddustattractedtothe
chargedmonitor?Well,whenweusethecomputer,extraelectronsonthe
surfacebuildup.Thentheseelectronsmaketheelectronsintheparticlesofdust
moveawaybecauselikechargesrepel.Asaresulttherearemorepositive
chargesinthedustparticlesclosetothemonitorandasoppositechargesattract,
thedustisattractedtothemonitor.
Fig.2.1.Achargedmonitorscreenattractsunchargedparticlesofdust
Chargeswhich‘appear’ontheparticlesofdustarecalledinducedcharges
andtheprocessiscalledelectrostaticinduction.Gold-leafelectroscopeisan
instrumentfordetectingcharge.Itsprincipleofoperationisbasedonthe
phenomenonofelectrostaticinduction.Thisinstrumenthasagold-leafwhich,if
theinstrumentischarged,movesawayfromthecentralroditisattachedto.The
instrumentischargedbyinduction,whichmeans‘atadistance’thatiswhenthe
chargedbodydoesnottouchtheinstrumentbutonlyisputcloselytoit.
