把一个定值电阻和一个滑动变阻器串联起来后，电源电压不变，当移动变阻器时，变阻器 （2013?朝阳区一模）将定值电阻R1和滑动变阻器R2串联后...
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当电源电压不变时,一个定值电阻和一个滑动变阻器串联,滑动变阻器的滑片要先滑到电阻最大的地方，使电路中电流最小，起到保护作用！！随电阻变大变小，而变大变小。
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