题目内容
如右图所示,电源电动势为E,内电阻为r。当滑动变阻器R的滑片P从右端滑到左端时,发现电压表V1、V2示数变化的绝对值分别为ΔU1和ΔU2,下列说法中正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435300886.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435300886.png)
A.小灯泡L1、L3变暗,L2变亮 |
B.小灯泡L3变暗,L1、L2变亮 |
C.ΔU1>ΔU2 |
D.ΔU1<ΔU2 |
BC
试题分析:AB、当滑动变阻器R的滑片P从右端滑向左端时,滑动变阻器R接入电路的电阻减小,闭合电路总电阻减小,通过电源的电流增大,路端电压U减小,流过
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435316349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435316349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435316349.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435363382.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435378355.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435378355.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435410506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435425320.png)
CD、由
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435441628.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003435472621.png)
故选BC
点评:中等难度。动态问题分析思路总体来说是按照先部分后整体再部分的顺序,要充分利用电路中不变部分的电阻不变的特点,间接地讨论电路变化部分.还要注意电源是有内阻的。
![](http://thumb2018.1010pic.com/images/loading.gif)
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