题目内容
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_ST/images0.png)
①使电荷量Q、正对面积S一定,增大两板间距离d则静电计指针偏角 (填“变大”、“变小”或“不变”);
②使电荷量Q、两板间距离d、正对面积S一定,在两极板间放入石蜡,则静电计指针偏角 (填“变大”、“变小”或“不变”).
【答案】分析:根据电容的决定式C=
,分析电容如何变化,由电容的定义式C=
分析板间电压的变化,再判断静电计指针偏角的变化.
解答:解:
①增大两板间距离d,由电容的决定式C=
可知,电容变小.电荷量Q一定,由电容的定义式C=
分析可知,板间电压变大,则静电计指针偏角变大.
②两板间距离d、正对面积S一定,在两极板间放入石蜡,由电容的决定式C=
可知,电容变大.电荷量Q一定,由电容的定义式C=
分析可知,板间电压变小,则静电计指针偏角变小.
故答案为:变大,变小
点评:本题是电容器动态变化分析问题,关键要掌握电容的决定式C=
和电容的定义式C=
,并能进行综合分析.
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/1.png)
解答:解:
①增大两板间距离d,由电容的决定式C=
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/2.png)
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/3.png)
②两板间距离d、正对面积S一定,在两极板间放入石蜡,由电容的决定式C=
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/4.png)
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/5.png)
故答案为:变大,变小
点评:本题是电容器动态变化分析问题,关键要掌握电容的决定式C=
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/6.png)
![](http://thumb.1010pic.com/pic6/res/gzwl/web/STSource/20131029193339162562562/SYS201310291933391625625017_DA/7.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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