题目内容
如图所示,电路A、B两点分别接恒压电源的正、负极,滑动变阻器R的最大阻值为3R0,ab=bc=cd,伏特表的内阻Rv 的阻值为2R0,水平放置的平行金属板长为L、极板间距为d,且d=
,极板间电场均匀分布.现有一个质量为m、电量大小为q的粒子以大小为
的初速度从下极板边缘飞入匀强电场,当滑片p处于a点时,粒子恰好从上极板边缘水平飞出,粒子重力不计.求
(1)粒子的带电性质及
与水平极板间的夹角θ;
(2)恒压电源的电压U;
(3)若保持
大小不变但改变
方向,使得带点粒子恰能沿极板中央轴线水平飞出,这时伏特表的读数多大?滑片p 应处于哪个位置?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241330197893372.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019414394.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019461308.png)
(1)粒子的带电性质及
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019461308.png)
(2)恒压电源的电压U;
(3)若保持
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019461308.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019461308.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241330197893372.png)
(1)正电θ=45o(2)
(3)Rx≈2.7Ro
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019945988.png)
(1)粒子带正电 (2分)
分运动时间相等
(2分)
θ="45o" (1分)
(2)
(2分)
y=d, 电压
(1分)
(3)y=
,由分运动时间相等
得tg
=
(1分)
, 相应的伏特表读数
(2分)
由分压关系知滑片P应处于ab之间(1分),滑动变阻器滑片P以下部分电阻为Rx≈2.7Ro (1分)
分运动时间相等
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019992920.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020054696.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241330201011684.png)
y=d, 电压
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133019945988.png)
(3)y=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020350428.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020491933.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020709330.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020756338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020787664.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133020818849.png)
由分压关系知滑片P应处于ab之间(1分),滑动变阻器滑片P以下部分电阻为Rx≈2.7Ro (1分)
![](http://thumb2018.1010pic.com/images/loading.gif)
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