如图所示,电源电压为8V,电阻R1=4R2,电流表的示数为0.2A;求电阻R1和R2的电阻值各为多少欧姆?

问题描述:

如图所示,电源电压为8V,电阻R1=4R2,电流表的示数为0.2A;求电阻R1和R2的电阻值各为多少欧姆?

(1)∵I=

U
R
,∴电路总电阻R=
U
I
=
8V
0.2A
=40Ω;
(2)两电阻并联,则
1
R
=
1
R1
+
1
R2
=
1
4R2
+
1
R2
=
5
4R2

R2=
5
4
R=
5
4
×40Ω=50Ω,R1=4R2=4×50Ω=200Ω;
答:电阻R1和R2的电阻值分别是200Ω与50Ω.