题目内容
有一带电量q=-3×10-6C的点电荷,从电场中的A点移到B点时,克服电场力做功6×10-4J.从 B点移到C点时电场力做功9×10-4J.问:
⑴AB、BC、CA间电势差各为多少?
⑵如以B点电势为零,则A、C两点的电势各为多少?电荷在A、C两点的电势能各为多少?
⑴AB、BC、CA间电势差各为多少?
⑵如以B点电势为零,则A、C两点的电势各为多少?电荷在A、C两点的电势能各为多少?
(1)
,
,
(2)200V,300V -6×10-4J, -9×10-4J
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130597678.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130628682.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130644643.png)
⑴先求电势差的绝对值,再判断正、负
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051306591150.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130675515.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130706788.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051307221559.png)
因负电荷从B移到C电场力做正功,必是从低电势点移到高电势点,即
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130737466.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130753678.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250051307842570.png)
⑵若
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130800413.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130815584.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130831702.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130847568.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005130878850.png)
,电荷在A点的电势能 EA="qφA=-3×10-6×200" J=-6×10-4J
电荷在C点的电势能 Ec="qφC=-3×10-6×300" J=-9×10-4J.
![](http://thumb2018.1010pic.com/images/loading.gif)
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