额定电功率：P(b)=U^2/R(b)=2*P(a)=2*U^2/R(a)
R(a)=2*R(b)
实际a分得电压：U(a)=U*R(a)/[R+R(a)]
电功率：P(a)=U²*R(a)/[R+R(a)]²=13.5w ①
实际b分得电压：U(b)=U*R(b)/[R+R(b)]
电功率：P(b)=U²*R(b)/[R+R(b)]²=17.28w ②
①②联立解得额定电压P(b)=48w
P(a)=24w