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在“电磁振荡”一节的教学中,要使学生明确电磁振荡的概念,关键是做好演示实验,使学生能直接看到一个 “大小和方向都作周期性变化的电流”.那么就能给学生留下直观、深刻的印象.同时,教师讲解这一概念也就有了基础.为了达到这一目的,我把课本上的演示电路改成图1所示.由于采用了电磁开关K,它每秒可扳动50次.从而在示波器的荧光屏上显示出一个稳定而没有闪烁感的电磁振荡的波形.取得了十分令人满意的效果.
In the teaching of “electromagnetic oscillations”, to make students clear about the concept of electromagnetic oscillations, the key is to do demonstration experiments so that students can directly see a “current that changes periodically in size and direction.” This will give the student an intuitive and profound impression. At the same time, the teacher will have a basis for explaining this concept. To achieve this goal, I changed the demonstration circuit in the textbook to that shown in Figure 1. Electromagnetic switch K, which can be flipped 50 times per second, thus showing a stable and no flicker of the electromagnetic oscillation waveform on the oscilloscope’s fluorescent screen, and achieved very satisfactory results.