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在当前普通中学里,作教学演示用的直流电流计,灵敏度低、输入阻抗小。如果用它去测量感生电流或光电流之类的弱电流,就显得很困难。在实际教学中,教师们往往是用多匝矩形线圈的一条边当作一根导线去演示直线导体切割磁力线;在讲述楞次定律时,为了讲清感生电流的流向同,得不在多匝,多层的线圈的外层加绕几圈有颜色的塑料丝以表示螺线管的绕向。用上述的方法去做演示实验是很不直观的,它无疑给学生增添了听课的难度。
In the current ordinary secondary schools, the DC ammeter used for teaching demonstration has low sensitivity and small input impedance. If it is used to measure the induced current or light current like weak current, it becomes very difficult. In the actual teaching, teachers often use one side of the multi-turn rectangular coil as a wire to demonstrate the linear conductor cutting magnetic field lines. In the Lenz's law, in order to clarify the flow of induced current, , The outer layer of the multi-layer coil plus a few laps of colored plastic wire to indicate the direction of the solenoid. Using the above method to do demo experiments is not intuitive, it will undoubtedly add to the difficulty of listening to students.