先求出：L1电阻R1＝U^2/W＝6^2/3=12Ω L2电阻R1＝U^2/W＝12^2/3＝48Ω
并联时,两灯电压相等 U1＝U2
L1功率W1＝U1^2/R1＝6^2/12＝3瓦 L2功率W2＝Ub^2/Rb＝6^2/48＝0.75瓦
推导出L1亮