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现行初中物理教材中,关于焦耳定律的(定性)演示实验,不仅需要时间长(一般需5分钟之多)、电压高,而且在进行电流产生的热量和电流强度及通电时间之间的关系的两次实验中,都需要看表计时并与记忆中的前一次效果相比较,不能通过一次性对比得出结论,从而影响了教学效果。为了克服以上不足,我们利用气体热膨胀的原理,制作了如下图所示的焦耳定律演示器,在教学中应用收到了较为理想的效果。
In the current junior middle school physics textbook, the (qualitative) demonstration experiment of Joule’s law not only takes a long time (usually takes 5 minutes), but also has a high voltage, and it is related to the relationship between the current generated heat and the current intensity and the power-on time. In both experiments, it is necessary to look at the timing of the watch and compare it with the previous effect in the memory. It is not possible to draw conclusions through a one-time comparison, thereby affecting the teaching effect. In order to overcome the above deficiencies, we used the principle of gas thermal expansion to produce the Joule law demonstrator as shown in the figure below. The application in teaching has received satisfactory results.