The copper tube has a slot through which you can see two metal plugs which are small enough to slide freely in the tube. One of the plugs is a magnet. The other is not magnetized. The unmagnetized plug falls freely, while the magnetized plug falls very slowly. The moving magnet induces a current in the copper which is dissipated by electrical resistance to heat. This energy sink is the reason for slow motion.


Lenz’s Law