Demonstrate the phenomenon that DC power generates a magnetic field around it through a wire, and the relationship between the direction of the magnetic field and the direction of the current. The solenoid magnetic field demonstrator replaces the single-stranded wire with a multi-turn to increase the magnetic induction and enhance the demonstration effect. The instrument is made of a transparent material and should avoid friction and maintain its transparency. During the demonstration, after the magnetic induction line is formed, the power should be cut off to avoid excessive temperature and damage the instrument. After the experiment, the iron powder is brushed with a brush. The solenoid magnetic field uses a solenoid to demonstrate the external circuit. After energization, the iron powder around the solenoid is arranged in a magnetic sense line according to the direction of the magnetic field. The small magnetic needle is placed at each position to verify the direction of the magnetic field. . Changing the direction of the current, the direction of the magnetic induction line also changes, and the relationship of the direction is also in accordance with the right-handed screw rule.