题目内容
如图所示,实线为电场线,虚线为等势线,且相邻两条等势线间的电势差相等。一正电荷(只在电场力的作用下)在φ3上时,具有的动能是20eV,它运动到等势线φ1上时,速度为零。令φ2=0。那么该电荷的电势能为4 eV时,其动能大小为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020275793102.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250020275793102.jpg)
A.16eV | B.6eV | C.10eV | D.4eV |
B
试题分析:因为只有电场力做功,所以动能和电势能之和不变,又因为正电荷从等势线φ3运动到等势线φ1时,动能减小,所以电场线方向向右,正电荷在等势线φ1的电势能为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027595651.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027611501.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027626639.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027626673.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027642614.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027657702.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027673616.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002027689822.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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