题目内容
(14分)一电路如图所示,电源电动势
,内阻
,电阻
,
,
,C为平行板电容器,其电容C=3.0pF,虚线到两极板距离相等,极板长
,两极板的间距
。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455095163092.png)
(1)若开关S处于断开状态,则当其闭合后,求流过R4的总电量为多少?
(2)若开关S断开时,有一带电微粒沿虚线方向以
的初速度射入C的电场中,刚好沿虚线匀速运动,问:当开关S闭合后,此带电微粒以相同初速度沿虚线方向射入C的电场中,能否从C的电场中射出?(要求写出计算和分析过程,g取
)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145508268576.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145508502496.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145508721558.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145508783622.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145508830555.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145509001543.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145509111659.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455095163092.png)
(1)若开关S处于断开状态,则当其闭合后,求流过R4的总电量为多少?
(2)若开关S断开时,有一带电微粒沿虚线方向以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145509610637.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145509672520.png)
(1)
(2)微粒不能射出
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145509719633.png)
试题分析:(1)S断开时,电阻R3两端电压为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455097811102.png)
S闭合后,外阻为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455098281047.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145509891900.png)
电阻R3两端电压为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455099841014.png)
则所求流过R4的总电量为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455100471122.png)
(2)设微粒质量为m,电量为q,当开关S断开时有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145510109794.png)
当开关S闭合后,设微粒加速度为a,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145510468952.png)
设微粒能从C的电场中射出,则水平方向:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145510515512.png)
竖直方向:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145510577645.png)
由以上各式求得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241455107171021.png)
故微粒不能射出
点评:本题学生明确开关断开和闭合时电路中各电阻的连接方式,电容器两极板间的电压变化,进而求出电荷量的变化;第二问微粒做类平抛运动,可按平抛运动的方法去分析。
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目