2.电势叠加原理 P. V=Σy, 99 [来历]V=rE=②E,)i=∑E, =】 2.电势叠加原理 V = Vi   =  P V E dl   [来历] N q q1 2 q i q P Vi =   =   P i E dl   ( )   =   P i E dl  