题目内容
光滑绝缘水平面上有一个带点质点正在以速度
向右运动。如果加一个竖直向下的匀强磁场,经过一段时间后,该质点的速度第一次变为与初始时刻的速度大小相等、方向相反;如果不加匀强磁场而改为加一个沿水平方向的匀强电场,经过相同的一段时间后,该质点的速度也第一次变为与初始时刻的速度大小相等、方向相反,则所加的匀强磁场的磁感应强度
和所加的匀强电场的电场强度
的比值
为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250032568641065.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256786265.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256802309.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256817318.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256833438.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250032568641065.png)
A.![]() | B.![]() | C.![]() | D.![]() |
A
试题分析:带电质点在磁场中做匀速圆周运动,满足:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256927608.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256942761.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256958518.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256973702.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003256989653.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003257005609.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003257020406.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003257036899.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003257051684.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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