题目内容
某个分压电阻串接在电压表上,使测量电压的量程扩大到n倍;另一个分压电阻串接在电压表上,量程扩大到m倍.如果把这两个电阻并联后再串接到该电压表上,它的量程将扩大到( )?
A.![]() | B.![]() |
C.(m+n)倍? | D.|m-n|倍 |
A
试题分析:串联电阻有分压作用,给电压表串联一个电阻可扩大量程,由部分电路欧姆定律有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151837980851.png)
设电压表内阻为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151838089372.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151838167340.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151838214875.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151838277915.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241518384331259.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151838557778.png)
故选A
点评:注意电表的改装中表头的最大电压和电流是不变的。
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目