题目内容
如图1所示,厚度均匀的矩形金属薄片边长ab=10 cm,bc=5 cm.当将A与B接入电压为U的电路中时,电流为1 A;若将C与D接入同一电路中,则电流为 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241415013092269.png)
A.4 A | B.2 A | C.![]() | D.![]() |
A
首先计算出沿A、B方向和沿C、D方向电阻的比值,再利用欧姆定律求出两种情况下的电流比.设沿A、B方向的横截面积为S1,沿C、D方向的横截面积为S2,则
=
,A、B接入电路中时的电阻为R1,C、D接入电路中时的电阻为R2,则有
=
=
.两种情况下电流之比为
=
=
,故I2=4I1=4 A.选项A正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501480464.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501356338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501761452.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501824904.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501870307.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501917412.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501964458.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141501434303.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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