在做电磁感应现象实验时,因受条件限制,找不到大蹄形磁铁,只好用小蹄形磁体来做实验。由于产生的感应电流太小,电表指针摆动的幅度很小,用灵敏电流计代替演示电表时,其可见度小,后排同学无法看清指针的偏转变化情况,影响了实验效果。后来,笔者用投影仪来显示指针偏转情况,取得了令人满意的效果。具体做法是:先取下灵敏电流计底盘上的铝板和垫纸, In the electromagnetic induction phenomenon experiment, due to limited conditions, no big magnets could be found, and they had to use small hoop-shaped magnets for experiments. Because the induced current is too small, the swing of the meter pointer is very small. When the sensitive ammeter is used instead of the demo meter, the visibility is small, and the rear classmate cannot see the deflection of the pointer, which affects the experimental results. Later, I used a projector to show the deflection of the pointer and achieved satisfactory results. The specific approach is: first remove the aluminum plate and pad of the sensitive galvanometer chassis,