题目内容
(8分)某实验小组要测定一电源的电动势E和内电阻r。实验器材有:一只DIS电流传感器(可视为理想电流表,测得的电流用I表示),一只电阻箱(阻值用R表示),一只开关和导线若干.该实验小组同学设计了如图甲所示的电路进行实验和采集数据.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250052426856511.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250052427006092.jpg)
(1)小组设计该实验的原理表达式是________(用E、r、I、R表示);
(2)小组在闭合开关之前,应先将电阻箱阻值调至________(选填“最大值”、“最小值”或“任意值”),在实验过程中,将电阻箱调至图乙所示位置,则此时电阻箱接入电路的阻值为______Ω;
(3)小组根据实验采集到的数据作出如图丙所示的
-R图象,则由图象求得,该电源的电动势E=________V,内阻r=________Ω(结果均保留两位有效数字).
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250052426856511.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250052427006092.jpg)
(1)小组设计该实验的原理表达式是________(用E、r、I、R表示);
(2)小组在闭合开关之前,应先将电阻箱阻值调至________(选填“最大值”、“最小值”或“任意值”),在实验过程中,将电阻箱调至图乙所示位置,则此时电阻箱接入电路的阻值为______Ω;
(3)小组根据实验采集到的数据作出如图丙所示的
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242716300.png)
(1)
(2)最大值 25 (3)6.0(5.8~6.2均可) 2.4(2.3~2.5均可)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242732631.png)
试题分析:(1)由图可知,本实验采用的是电流表与电阻箱测定电动势,在闭合电路中,电动势:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242732631.png)
(2)为了保证电路安全,闭合开关前电阻箱接入电路的阻值应为电阻箱的最大阻值;由图乙所示电阻箱可知,电阻箱的示数为:0×1000Ω+0×100Ω+2×10Ω+5×1Ω=25Ω;
(3)在闭合电路中,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242732631.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242778683.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242794426.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242810528.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242825495.png)
由图象可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250052428411305.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242856781.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242872557.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825005242888549.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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