如图所示为某种电子秤的原理示意图，AB为一均匀的滑线电阻，阻值为R，长度为L，两

发布时间：2017-06-02 08:51 │ 来源：www.tikuol.com

题型：计算题

问题：

如图所示为某种电子秤的原理示意图，AB为一均匀的滑线电阻，阻值为R，长度为L，两边分别有P₁、P₂两个滑动头，P₁可在竖直绝缘光滑的固定杆MN上保持水平状态而上下自由滑动，弹簧处于原长时，P₁刚好指着A端，P₁与托盘固定相连。若P₁、P₂间出现电压时，该电压经过放大，通过信号转换后在显示屏上将显示物体重力的大小。已知弹簧的劲度系数为k，托盘自身质量为m₀，电源电动势为E，内阻不计，当地的重力加速度为g。求：

（1）托盘上未放物体时，在托盘自身重力作用下，P₁离A的距离x₁；

（2）托盘上放有质量为m的物体时，P₁离A的距离x₂；

（3）在托盘上未放物体时通常先校准零点，其方法是：调节P₂，使P₂离A的距离也为x₁，从而使P₁、P₂间的电压为零。校准零点后，将物体m放在托盘上，试推导出物体质量m与P₁、P₂间的电压U之间的函数关系式。

考点：实验：传感器的应用

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阅读短文，用方框内所给单词的正确形式填空，使短文意思通顺、完整。请将答案写在短文后相应题号的横线上。注意：①每个词只能用一次。②每空限填一词，有些词需要做相应的变化。③其中有两个多余选项。

leave decide then day lunch get one few eye happy stop read

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to turn back to my hotel for   5   I decided I had better ask the way. The trouble was that the only word I knew
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by the arm. There was a strange look in his   8 as he pointed left and right and left again. I thanked him politely
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on either side of me. I had come all the way into the country. The thing  10 for me to do was to find the
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1._________    2._________    3._________   4._________   5._________
6._________   7._________    8._________    9._________ 10._________

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