题目内容
(16分)如图所示,相距为2d的A和B两点上固定着等量异种的两个点电荷,电荷量分别为+Q和-Q.在AB连线的中垂线上取一点P,垂足为O,∠PAO=α,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009335012870.jpg)
(1)-Q在P点的场强的大小和方向;
(2)P点的场强的大小和方向;
(3)α为何值时,P点的场强最大,其最大值是多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009335012870.jpg)
(1)-Q在P点的场强的大小和方向;
(2)P点的场强的大小和方向;
(3)α为何值时,P点的场强最大,其最大值是多少?
(1)
由P指向B (2)
方向向右(3)0,
,方向向右
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000933517799.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000933533878.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000933548670.png)
试题分析:⑴负电荷在P点产生场强大小为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000933564674.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009335951245.png)
方向:由P指向B
⑵如图所示,P点场强是正、负电荷在P点产生场强的矢量和,由图得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009336114687.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009336262001.png)
⑶由上式表明,当α=0时,得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000933642996.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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