如图 图中电压表V1与V2示数之比为3:5 乙图中电流表A1与A2的示数之比为5:9求R1:R2:R3
1个回答

当图中是电压表时,V1:V2=(R1+R2):(R2+R3)=3:5 -------(1)

当图中是电流表时,I1:I2=R12:R23

=R1R2/(R1+R2):R2R3/(R2+R3)

=R1R2(R2+R3)/R2R3(R1+R2)

=R1/R3*(R2+R3)/(R1+R2)=5:9 --------(2)

(1)式代入(2)式得 (R1:R3)*5/3=5:9

所以 R1:R3=1:3 ,将这个关系式代入(1)式可得 R1:R2=1:2

所以 R1:R2:R3=1:2:3