题目内容
有两个电压表VA和VB,量程已知,内阻不知,另有一干电池,其内阻不能忽略但不知多少,只用这两个电压表、开关和导线,能通过测量计算出这个电池的电动势(已知电动势不超过电压表量程,干电池不许拆开),导出用测量值计算电动势的关系式。
E=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412093799373.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938071871.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412093799373.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938071871.gif)
如图a,两个电压表串联测得读数分别为
、
再用图b,分别
用两表测得读数分别为UA、UB,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209381184620.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412093799373.gif)
①
②
由图a得
③
解①②③式得E=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412093799373.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938071871.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938086280.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938102300.gif)
用两表测得读数分别为UA、UB,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241209381184620.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412093799373.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938149936.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938180944.gif)
由图a得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938196593.gif)
解①②③式得E=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412093799373.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120938071871.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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