二.RLC串联电路的功率 瞬时功率 p=ui=v2U sin( ot+y)v2Isin( ot+y. UI cos(yu -vi)-UI cos(2ot +yu=Y,) UI cos (p-UI cos(2ot +op) 平均功率(有功功率) P=pt=J[UI cos (-UI cos(2ot+o)]dt TO TO UI COSO=UD=I'R=OR R二. RLC串联电路的功率 瞬时功率 UI cos UI cos(2 t ) UI cos( ) UI cos(2 t ) p ui 2Usin( t ) 2Isin( t ) u i u i u i             = − + = − − + − = = + + 平均功率（有功功率） UI UI t dt T pdt T P T t [ cos cos(2 )] 1 1 0 0 =  =  −  +  R U UI IU I R R R 2 2 = cos = = =