Treść książki
Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
20
aconductingpath,aswitchandaload.ThesourceofEMFcanbeacell.
Acommonwordforacellisabattery.Abattery,infact,isasetofcells.
Aconductingpathisusuallyawireandaloadisanelectriccomponenttowhich
AsimplecircuitconsistsofthesourceofEMF(electromotiveforce),
ASimpleCircuit
PartI
powerisdelivered,forexample,alightbulb.Aswitchisadevicewhichisused
forclosingoropeningacircuit.Ifthecircuitisclosed,theelectronscanflowfrom
thenegativecellterminaltothepositivecellterminal.Ifthecircuitisopen,there
isagapinthewireandtheelectronscannotflow.
Electronsflowfromthenegativecellterminaltothepositiveone.However,
theconventionalcurrentdirectionisfromthepositiveterminaltothenegativeone.
Thisisbecausescientistsdefinedthedirectionofcurrentflowbeforethey
discoveredtheelectron.Mathematically,theprocessesarethesame.
Theflowofelectronsinacircuitiscalledcurrent.TheSIunitofcurrentis
ampere(A).Oneampereisequaltoaflowofonecoulombpersecond,oraflow
of6.24×10
18electronspersecond.Currentsaremeasuredwithameasuring
devicecalledanammeter.Inordertomeasurecurrentwehavetoopenthe
circuitandconnecttheammeterinthecurrentpath:Thepositiveammeter
terminalshouldbeonthesamesideasthepositivecellterminalandthenegative
ammeterterminalshouldbeonthesamesideasthenegativecellterminal.This
iscalledaseriesconnection.
StudentA:
a.Whatdoesaswitchdotoacircuit?
b.Whatisanothernameforabattery?
c.Whatistherealdirectionofcurrentflow?
d.Whatis1ampere?
e.Howdoyouconnectanammetertoacircuit?
StudentB:
a.Whatdoesacircuitconsistof?
b.Whatisaload?
c.Whatiscurrent?
d.Whatistheconventionaldirectionofcurrentflow?
e.Whatdoesanammetermeasure?
