题目内容
如图所示,电动势为E、内阻为r的电池与滑动变阻器R串联,已知滑动变阻器的最大阻值是r.当滑动变阻器的滑片P由a端向b端滑动时,下列说法中正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250034374691163.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250034374691163.png)
A.滑动变阻器消耗的功率不变 |
B.滑动变阻器消耗的功率变大 |
C.内阻上消耗的功率变小 |
D.滑动变阻器消耗的功率变小 |
D
试题分析:根据闭合电路欧姆定律得:总电流
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003437484616.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250034375001422.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003437516384.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003437547468.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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