(1)串联:0.075=U/(40+R2)并联:0.3=U/40+U/R2联立求解R2=40ΩU=6V(2)P串=U^2/(R1+R2)=U^2/80P并=U^2/R1+U^2/R2=U^2/20P串/P并=1/4第二问实际上就是功率之比