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1、维修电工基础知识（Basicknowledgeofmaintenanceelectrician）Basicknowledgeofelectricalengineeringandbasicknowledgeofmaintenanceelectrician.(1)resistivity--alsocalledresistancefactororspecificresistance.IsameasureoftheperformanceofconductivematerialwiththeletterP,saidthattheunits
2、ofohms*mm/squaremeters.Innumericalterms,equaltothematerialtodo1meterslong,crosssectionalareaof1squaremillimetersofwire,atthetemperatureof20Cresistance,thegreatertheresistivity,thelowerconductivity.Thephysicalquantityoftheresistivityofasubstancevarieswithtemperature,a
3、nditsvalueisequaltotheratiooftheincreaseinresistivitytotheoriginalresistivity,atanincreaseof1C,usuallyinalphaalpha,1/C.2,thetemperaturecoefficientofresistance,physicalquantitiesoftheelectricalresistivityofthematerialvarieswithtemperature,thetemperatureisincreasedwhen
4、the1Cvalueisequaltotheratioofincrease,theresistivityandtheoriginalresistivity,usuallyexpressedinlettersofalpha,unitis1/C.3,conductance----theabilityofanobjecttoconductelectriccurrentiscalledconductance.IntheDCcircuit,thenumericalvalueofresistanceisthereciprocalconduc
5、tance,withtheletterandsaid,inunitsofohms.4,conductivity--alsoknownasconductivitycoefficient,isalsoameasureofphysicalconductivityofagoodorbadphysicalquantity.Thesizeisthereciprocaloftheresistivityinnumericalterms.Theunitism/ohm*mmsquared.5electromotiveforce----thepote
6、ntialdifferencecausedbytheconversionofotherformsofenergyintoelectricenergyinacircuitiscalledelectromotiveforceorpotential.TheletterEstandsforvolts.6,self-whenthecurrentclosedloopchanges,thecurrentgeneratedbythecircuititselfthroughthefluxalsochanges,sointheloopwillals
7、oinducedelectromotiveforce,thisphenomenoniscalledselfinductancephenomenon,theinducedelectromotiveforcecalledelectromotiveforce.7mutualinductance-iftwocoilsareclosetoeachother,thefluxofthecurrentinthefirstcoilispartlyconnectedtothesecondcoil.Whenthecurrentinthefirstco
8、ilchanges,thenthefluxofthecoillinkwiththesecondcoilisalsochanged,andtheinducedelectromotiveforceisgeneratedinthesecondcoil.Thisphen
