0.3A（并联电阻为20Ω）9V（两电阻分压为3V和6V）--------------------------------------------I1＝U/R1＝6/30＝0.2AI2＝U/R2＝6/60＝0.1A并联时：I＝I1＋I2＝0.3A串联时：I＝min(I1,I2)＝I2＝0.1A,U＝I·(R1＋R2)...