题目内容
(14分)有一种测量压力的电子秤,其原理如图(甲)所示。E是内阻不计、电动势为6V的电源。R0是一个阻值为400
的限流电阻。G是由理想电流表改装成的指针式测力显示器。R是压敏电阻,其阻值可随压力大小变化而改变,其关系如下表所示。C是一个用来保护显示器的电容器。秤台的重力忽略不计。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015275604557.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015275751665.jpg)
(1)在如图(乙)所示的坐标系中画出电阻R随压力F变化的图线,并归纳出电值R随压力F变化的函数关系式。
(2)写出压力与电流的关系式,说明该测力显示器的刻度是否均匀。
(3)若电容器的耐压值为5V,该电子秤的量程是多少牛顿?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527513289.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015275604557.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015275751665.jpg)
压力F/N | 0 | 50 | 100 | 150 | 200 | 250 | 300 | ...... |
电阻R/![]() | 300 | 280 | 260 | 240 | 220 | 200 | 180 | ...... |
(2)写出压力与电流的关系式,说明该测力显示器的刻度是否均匀。
(3)若电容器的耐压值为5V,该电子秤的量程是多少牛顿?
(1)如图所示:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015276062828.png)
电值R随压力F变化的函数关系式为:
或
。
(2)
,显示器的刻度不均匀。
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527684588.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250015276062828.png)
电值R随压力F变化的函数关系式为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527622602.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527653656.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527684905.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527684588.png)
试题分析:
(1)要求用描点法画成直线,如答案图所示 (2分)
由图可知R与F成线性关系,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527622602.png)
或
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527653656.png)
(2)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527731659.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527622602.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527684905.png)
F与I不成线性关系,所以刻度不均匀 (2分)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001527684588.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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