Question

现有两个电阻,串联后的电阻为R,并联后的电阻为r,令R=tr,则实数t的取值范围是

Answer 1

电阻R1,R2

串联R=R1+R2

并联1/r=1/R1+1/R2 r=R1*R2/(R1+R2)

t=R/r=(R1+R2)^2/(R1*R2)

MIN :R1=R2 R1*R2->MAX t=(R1+R1)^2/(R1*R1)=4

MAX:R1->0 t=R2/0 趋向无穷 (同理R2)

取值范围[4,+oo)