题目内容
如图所示电路,已知R1=3 kΩ,R2=2 kΩ,R3=1 kΩ,I=10 mA,I1=6 mA,则a、b两点电势高低和通过R2中电流正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411009282548.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411009282548.png)
A.a比b高,7 mA | B.a比b高,2 mA |
C.a比b低,7 mA | D.a比b低,2 mA |
C
本题考查电流守恒定律,即流入某节点的电流一定等于从该节点流出的电流,如图所示:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411009751701.png)
I3=I-I1=10 mA-6 mA=4 mA
Uca=I1R1=6×10-3×3 V=18 V
Ucb=I3R3=4×10-3×1 V=4 V,Ub>Ua
I2=
=
mA=7 mA,所以选项C正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241411009751701.png)
I3=I-I1=10 mA-6 mA=4 mA
Uca=I1R1=6×10-3×3 V=18 V
Ucb=I3R3=4×10-3×1 V=4 V,Ub>Ua
I2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141101021573.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141101084390.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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