题目内容
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241203551201482.gif)
如图所示,射线管阴极K发射电子,阳极P和阴极K间加上电压后电子被加速。.A、B是偏向板,使飞进的电子偏离.若已知P、K间所加电压U1,偏向板长L,板间距离d,所加电压U2.电子质量m,电子电量e.设从阴极出来的电子速度为0.求电子:
(1)经过P板时的速度υ0? (2)飞出偏转电场时的速率υt?
(3)电子最终到达距离偏向板为R的荧光屏上的O′点,此点偏离入射方向的距离Y是多少?
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355135597.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241203551351115.gif)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241203551511013.gif)
(1)由动能定理
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355166550.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355135597.gif)
(2)电子的加速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355291499.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355307290.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355322646.gif)
电子出电场时的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241203551351115.gif)
(3)电子出电场中的偏向角满足
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120355338710.gif)
电子可以看成是从极板中点飞出,故
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241203551511013.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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