题目内容
在测定电阻的实验中,通常有半偏法,替代法:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539236742267.jpg)
A
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539237203886.jpg)
B
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539240486629.jpg)
C
(1)在测电流表内阻Rg的实验中,使用如图A所示的电路,当S2断开,S1闭合,且R1调到9900Ω时,电流表指针满偏转到0.2mA,再闭合S2,将R2调到90Ω时,电流表指针正好指在刻度盘中央,则电流表的内阻Rg= Ω。此值较Rg的真实值是 。(填偏大、偏小或相等)
(2)在用替代法测电阻的实验中,测量电路如图B所示,图中R是滑动变阻器,Rs是电阻箱,Rx是待测高值电阻,S2是单刀双掷开关,G是电流表。
①按电路原理图将图C(图中已连好4根导线)所示的器材连成测量电路。
②实验按以下步骤进行,并将正确答案填在题中横线上。
A.将滑动片P调至电路图中滑动变阻器的最下端,将电阻箱Rs调至最大,闭合开关S1,将开关S2拨向位置"1",调节P的位置,使电流表指示某一合适的刻度IG。
B.再将开关S2拨向位置"2",保持 位置不变,调节 ,使电流表指示的刻度仍为IG。
假设步骤B中使电流表指针指示的刻度为IG时电阻箱的阻值为R0,则Rx= 。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539236742267.jpg)
A
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539237203886.jpg)
B
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539240486629.jpg)
C
(1)在测电流表内阻Rg的实验中,使用如图A所示的电路,当S2断开,S1闭合,且R1调到9900Ω时,电流表指针满偏转到0.2mA,再闭合S2,将R2调到90Ω时,电流表指针正好指在刻度盘中央,则电流表的内阻Rg= Ω。此值较Rg的真实值是 。(填偏大、偏小或相等)
(2)在用替代法测电阻的实验中,测量电路如图B所示,图中R是滑动变阻器,Rs是电阻箱,Rx是待测高值电阻,S2是单刀双掷开关,G是电流表。
①按电路原理图将图C(图中已连好4根导线)所示的器材连成测量电路。
②实验按以下步骤进行,并将正确答案填在题中横线上。
A.将滑动片P调至电路图中滑动变阻器的最下端,将电阻箱Rs调至最大,闭合开关S1,将开关S2拨向位置"1",调节P的位置,使电流表指示某一合适的刻度IG。
B.再将开关S2拨向位置"2",保持 位置不变,调节 ,使电流表指示的刻度仍为IG。
假设步骤B中使电流表指针指示的刻度为IG时电阻箱的阻值为R0,则Rx= 。
(1)
,偏小
(2)①如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539246727249.jpg)
②P,
, ![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924766336.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924064679.png)
(2)①如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539246727249.jpg)
②P,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924703338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924766336.png)
试题分析:(1)半偏法测电阻,当闭合
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924875375.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924937510.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153925312361.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924064679.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924875375.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153925312361.png)
(2)①电路连接原则:从正极到负极,先干路再支路,先串联再并联,连接电路如下图
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241539257957245.jpg)
②由欧姆定律可知,将开关
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924875375.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924703338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153926560343.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153926638355.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153926700456.png)
点评:注意半偏法测电阻时有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924937510.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153924875375.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153926903327.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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