题目内容
电动势为E、内阻为r的电源与定值电阻R1、R2及滑动变阻器R连接成如图所示的电路,当滑动变阻器的触头由中点滑向b端时,下列说法正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707286352865.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707286352865.jpg)
A.电压表和电流表读数都增大 | B.电压表和电流表读数都减小 |
C.电压表读数增大,电流表读数减小 | D.电压表读数减小,电流表读数增大 |
A
试题分析:当滑片向b滑动时,R接入电阻增大,总电阻增大;由闭合电路的欧姆定律可知电路中总电流减小,则内电压减小,由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170728713549.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170729212327.png)
故选A.
点评:本题中
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170729212327.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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