 I have some iron filings spread across and I have this U shaped magnet. So when I bring the magnet close to the filings, all the filings get attracted to the two poles of the magnet. Look at how many iron filings are stuck to the two poles. Now I have attached a metal plate to the two poles of the magnet and I will again see how many filings get attracted to the magnet. Well, most of them do. Not many are getting attracted to the ends of the north and south pole. Many are getting attracted to the sides. Let's compare that. So there are still many iron filings getting attracted even when there is a metal plate attached to the two poles. But we see no iron filings are getting stuck or are attracted to the two ends. So this shows that the effect of a magnet is slightly reduced when there is a metal plate in between the magnet and the iron filings. Now let's take a magnetic compass and again bring the U shaped magnet close to the compass. There is no metal plate to begin with. Let's see how the needle deflects. So when you bring it close, the needle deflects, right? And it deflected by a lot. Now let's attach the metal plate to it and now let's see how much the needle deflects. So even when we bring the magnet so close to the compass, there is no deflection. Now when the magnet is very close to the compass, there is some deflection. Not as much as there was when there was no metal plate in between the magnet and the compass. Let's compare. So the left image has a metal plate attached to the magnet and look at the amount of deflection. You can compare that with the image on the right where there is no metal plate. Even when there is some gap between the U shaped magnet and the magnetic compass, the amount of deflection in the right image is more than the amount of deflection in the left image. When there is a metal plate between the magnet and the magnetic substance that is a needle. So this again shows when there is a metal plate in between a magnet and a magnetic substance, then the effect of the magnet is reduced because of the metal plate in between.