题目内容
如图所示,在平行金属带电极板MN电场中将电荷量为- 4×10-6 C的点电荷从A点移到M板,电场力做负功8×10-4 J,把该点电荷从A点移到N板,电场力做正功为4×10-4 J,N板接地。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241525475581329.png)
求:(1)A点的电势
是多少?
(2)UMN等于多少伏?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241525475581329.png)
求:(1)A点的电势
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152547621387.png)
(2)UMN等于多少伏?
(1)-100V (2)-300V
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241525477141404.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152547823762.png)
∴
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152547964621.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241525480891584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152548198707.png)
∴
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152548307930.png)
则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241525484161039.png)
点评:在根据电场力做功求电势和电势差要注意各量的符号,并且要明确各符号代表的含义。
![](http://thumb2018.1010pic.com/images/loading.gif)
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