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三相交流电与生产实际联系紧密,学好这部分内容对学生以后的升学或直接参加生产建设都有重要意义。这部分教材有如下几个难点。需要在教学中注意克服: (一)三相平衡交流电的星形接法中性线为何可以去掉? 产生这个问题的症结在于不了解导体中有电流时电荷的运动情况。对此可引导学生回忆物质的导电性及振动和波的有关知识。当金属导线中有直流电通过时,其中的自由电子在热运动的基础上迭加了一个定向运动。当导线中通过交流电时,其中自由电子
The three-phase alternating current is closely related to the actual production. It is of great significance to learn this part of the content for the student’s further study or direct participation in production and construction. This part of the textbook has the following difficulties. It is necessary to pay attention in teaching to overcome: (a) Why can the neutral connection of a three-phase balanced alternating current star can be removed? The crux of this problem lies in the incomprehensibility of the movement of the charge when there is current in the conductor. This can guide students to recall the material’s conductivity and vibration and wave of knowledge. When a direct current passes through the metal wire, the free electrons therein are superimposed on an directional motion based on the thermal motion. When the wire passes through alternating current, the free electrons