在图中,总电流I=0.4安培,R1=R2=2欧姆,R3=1欧姆.则下列对通过R2的电流的判断中正确的是( )
A.向下通过0.1安培的电流
B.向上通过0.1安培的电流
C.向下通过0.2安培的电流
D.向上通过0.2安培的电流
![](https://img.ixiawen.com/uploadfile/2017/0419/20170419105008292.png)
(1)由电路图知:电阻R1、R2、R3并联,电流向上通过电阻R2;
(2)由并联电路的特点知:
=1 R并
+1 R1
+1 R2
,即:1 R3
=1 R并
+1 2Ω
+1 2Ω
,解得:R并=0.5Ω;1 1Ω
(3)并联电压U=IR=0.4A×0.5Ω=0.2V;
(4)由欧姆定律得,流过电阻R2的电流I2=
=U R2
=0.1A.0.2V 2Ω
故选B.