电源的电动势e=6v,内电阻r=1Ω,外电路电阻r1=6Ω,r2=12Ω,求

1与r2串联时：
1.路端电压：U=(r1+r2)e/(r1+r2+r)=5.68V
2.电源的输出功率:P=U^2/(r1+r2)=1.8W
r1与r2并联时：
r1和r2并联的总电阻：r'=r1*r2/(r1+r2)=4Ω
1.路端电压：U=r'e/(r'+r)=4.8V
2.电源的输出功率:P=U^2/r'=4.8^2/4=5.76W.