华东地区初三物理课本演示“通电螺线管的磁性”，适应课文右手螺旋定则的叙述方法，把螺线管的粗细画得和手握拳时的大小近似，每匝线圈的间距画得和手指间距差不多，但配备给实验室的仪器“电流磁场演示器”和课本上画的不同．若能做出和课本图上画得一样的螺线管，用铁屑演 The third-day physics textbook for East China demonstrates the “Magnetization of Energized Solenoids” and adapts to the narrative method of the right-handed spiral rule of the text. The thickness of the solenoid is approximated to the size of the fist, and the spacing of each coil is summed. The distance between the fingers is almost the same, but the instrument “current magnetic field demonstrator” equipped with the laboratory is different from the textbook. If you can make a solenoid that is the same as the picture on the textbook, use iron filings.