We're talking about induction/inductance/electromagnetic induction.
Question: dropping two cylinders through a metal pipe for which one is magnet, one drops quickly and the other slowly. Why?
The difference in the way the two cylinders behave when dropped through the metal pipe can be explained by the phenomenon of electromagnetic induction. When a magnet moves relative to a conductor (such as a metal pipe), it creates a changing magnetic field around the conductor. This changing magnetic field induces an electric current in the conductor, which in turn produces a magnetic field that opposes the motion of the magnet. This effect is known as Lenz's Law.
In this scenario, one of the cylinders is a magnet, while the other is not magnetic. The magnet creates a stronger changing magnetic field when it moves through the metal pipe compared to the non-magnetic cylinder. This stronger changing magnetic field induces a larger opposing electric current in the metal pipe, which generates a stronger magnetic field that opposes the motion of the magnet. As a result, the magnet experiences a greater amount of resistance or drag as it falls through the metal pipe, causing it to drop more slowly.
On the other hand, the non-magnetic cylinder does not generate a changing magnetic field as it moves through the metal pipe. Therefore, it does not induce as much opposing electric current and magnetic field in the pipe. As a result, the non-magnetic cylinder experiences less resistance or drag and falls more quickly.
To prove this concept experimentally, you can use a metal pipe and drop the magnet and non-magnetic cylinder separately. Observe their respective speeds and compare their behaviors. You should notice that the magnet falls more slowly due to the induction effects described above, while the non-magnetic cylinder falls relatively faster.