问题 填空题

某小组同学用小磁针、条形磁铁等按图8(a)、(b)的方法,探究了条形磁铁周围的磁场及方向。接着他们又用相同的方法,探究通电螺线管周围的磁场及方向,实验操作及现象如图8(c)、(d)、(e)所示。

(1)分析比较图8中的(c)与(d)或(c)与(e)可得出的初步结论是: (21)  

(2)分析比较图8中的(d)与(e)小磁针偏转情况可得出的初步结论是: (22)  

(3)分析比较图8中的(b)和(d)可得出的初步结论是:         (23)        

答案

(1)通电螺线管周围存在磁场;

(2)通电螺线管周围磁场的方向与通过的电流方向有关;

(3)通电螺线管周围的磁场形状与条形磁体周围的磁场现状相形

考点:磁场;通电螺线管的极性和电流方向的判断.

专题:应用题;图析法;转换法.

分析:(1)磁场的基本性质是对放入其中的磁体产生磁力的作用,若静止在南北方向上的小磁针发生偏转,说明了其周围有新的磁场产生.否则,则说明周围没有新的磁场产生.在磁场,小磁针偏转的方向发生了变化,说明说明磁场的方向发生了变化.

(2)根据题目要求,把握分析比较的两个图中的异同点,利用控制变量法的思路,即可得出结论.

解答:解:(1)在c图中,开关断开,电路中没有电流,小磁针的指向没有发生偏转,说明螺线管周围没有磁场.在d图中,开关闭合,小磁针的指向发生了偏转,说明通电螺线管的周围存在磁场.由此说明通电螺线管周围存在磁场.

(2)在d与e中,根据电源的正负极可知,电流方向不同,小磁针的指向不同,说明磁场方向不同,由此说明通电螺线管周围磁场的方向与通过的电流方向有关;.

(3)在bd两图中,通电螺线管周围小磁针的指向情况与条形磁体周围小磁针的指向情况相同,由此可知通电螺线管周围的磁场形状与条形磁体周围的磁场现状相同.

故答案为:(1)通电螺线管周围存在磁场;(2)通电螺线管周围磁场的方向与通过的电流方向有关;(3)通电螺线管周围的磁场形状与条形磁体周围的磁场现状相同

点评:(1)此题考查了通电螺线管周围的磁场的相关知识.

(2)认真审题,把握题目中要求比较的两个图的异同点是解决此题的关键.

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