Experimental principle: According to Faraday's law of electromagnetic induction, when a magnet moves relative to a metal material, an eddy current will be formed in the metal material, and the existence of the eddy current will hinder the relative movement between the magnet and the metal. The larger the eddy current, the stronger the obstacle. Under certain conditions, the strength of eddy current is closely related to the shape and size of the material.

Experimental steps: Let a magnet fall from the top of three hollow aluminum tubes (A, B, C) with a certain height, where A is an aluminum tube with a complete wall, B is an aluminum tube with a slit on the wall, and C is an aluminum tube with many round holes on the wall. Observe and compare the falling speed of the magnet under three conditions.

The experimental phenomenon is obvious: the magnet falls slowest in tube A, faster in tube C and fastest in tube B ... This is because the aluminum tube with complete tube wall contributes to the formation of eddy current, and the magnet is strongly hindered, so the magnet falls in it and moves slowest; For aluminum tubes with slits in the tube wall, eddy currents are not easy to form due to the blocking effect of the slits, and the magnets are weakly hindered, and the magnets fall quickly in them; Although the aluminum tube with many holes in the tube wall has the function of blocking eddy current, it is not as strong as the groove, so when the magnet falls inside, the movement speed is between A and B, which is faster than the complete tube wall and slower than the groove on the tube wall.