题目内容
将一个正点电荷从无穷远处移到电场中A点,电场力做功为4×10-9J,将一负点电荷(带电量与上述正点电荷相等)从无穷远处移到电场中的B点,克服电场力做功为8×10-9J,则下述结论中正确的是
A.jA<jB<0 | B.jB>jA>0 | C.jB<jA<0 | D.jA>jB>0 |
C
试题分析:由电场力做功跟电势能的关系
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145830944745.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145831240747.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241458314581020.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145831583736.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145831755741.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145831848996.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145832160583.png)
点评:本题学生明确在用电场力做功跟电势能的关系式和电势的定义式计算时,所用物理量在代入公式时要带正负号。
![](http://thumb2018.1010pic.com/images/loading.gif)
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