题目内容
某同学用刻度尺测金属丝的长度l,用螺旋测微器测金属丝的直径d,其示数分别如图1和图2所示,则金属丝长度l=________cm,金属丝直径d= mm。他还用多用电表按正确的操作程序测出了它的阻值,测量时选用“×1”欧姆挡,示数如图3所示,则金属丝的电阻R=_________Ω。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707333629660.png)
图1![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707336909106.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707333629660.png)
图1
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241707336909106.jpg)
(1)40.25±0.01 (2分)0.227±0.002 (2分)9
试题分析:(1)刻度尺的读数为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170733877576.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170734220488.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170735094614.png)
(2)螺旋测微器读数为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170735531954.png)
欧姆表的读数为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170735983611.png)
点评:螺旋测微器读数:先读固定刻度(只读整数,并注意是否露出半刻度线)再加上可动刻度(格数乘以0.01,注意格数需要估读)多用电表读数:当选用电流档和电压档时按电流表和电压表的读数方法读数,欧姆档读数是读出倍率再乘以档位即可,
![](http://thumb2018.1010pic.com/images/loading.gif)
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