题目内容
如右图所示,AC、BD为圆的两条互相垂直的直径,圆心为O,半径为R,将等电量的两正点电荷Q放在圆周上,它们的位置关于AC对称,与O点的连线和OC间夹角为30°,下列说法正确的是 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301115252381.jpg)
A.电荷q从A点运动到C点,电场力做功为零
B.电荷q从B点运动到D点,电场力做功为零
C.O点的场强大小为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130111556512.png)
D.O点的场强大小为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130111619608.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301115252381.jpg)
A.电荷q从A点运动到C点,电场力做功为零
B.电荷q从B点运动到D点,电场力做功为零
C.O点的场强大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130111556512.png)
D.O点的场强大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130111619608.png)
BD
电荷q从A点运动到C点,所受电场力竖直向上,电场力做负功,A错,根据对称性B正确,O点的场强大小为
,C错,D正确。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130111650988.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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