LENZ_Demo_Kit - Copper. The Lenz effect is a very popular science demonstration and all you need is a neodymium magnet to drop inside the pipe and - it works. The thickness of the copper pipe is very important in getting the magnet to slow down the most. This wall thickness is 0.080 inches compared to normal wall thickness of 0.028 inches. With the pipe 12 inches long it takes about 10 seconds for the magnet to float all the way down the pipe. The kit comes with an N50 ring magnet that is designed to perfectly fit and give the best float time. The ring magnet OD is 0.9449 inches and it is 0.394 inches thick.