自感现象是中学物理教学的一个难点,正确分析影响自感电动势大小的因素,对做好自感实验,准确解释自感现象十分重要.在如图1中如果两个并联分路的电阻相等,当开关K断开时,若断言能看到灯泡更亮一下的现象,并解释说:这是由于在断路的瞬间通过L的电流突然减小引起自感电动势,当L很大时,感应电动势就比原来电源的电动势大很多,灯泡当然就会突然变亮了.这样的判断和解释是不够正确的. The phenomenon of self-induction is a difficulty in physics teaching in middle schools. It is very important to properly analyze the factors that affect the size of the self-induced electromotive force, and it is very important to do self-induction experiments to accurately explain the phenomenon of self-induction. In Figure 1, the resistance of two parallel shunts is equal. When the switch K is turned off, if the assertion can see the phenomenon that the light bulb is brighter, it explains that this is due to a sudden decrease in the current through the L at the moment of disconnection, which causes a self-induced electromotive force. When L is large, the inductance The electromotive force is much larger than the original electromotive force, and the bulb will suddenly become brighter. Such judgments and explanations are not correct enough.