Why are the poles the strongest part of a magnet?

Answer 1

Ever notice how a magnet works? Oh, sure, it picks up paper clips or tacks, but what are the paper clips or tacks doing? What they are doing is trying to get "into the magnetic field" of the magnet. The magnetic won't really pick them up very well along its side, will it? Nope. You see that now. But it picks stuff well on the ends. Here's the scoop. The magnet has magnetic lines of force running through it (inside it), and these lines of force emerge from one pole (or end), curve around the body of the magnet, and re-enter the magnet at the other pole (or end). The density of the magnetic field outside the magnet is greatest at the poles ('cause that's where the lines of force leave and return). The lines of force will always do this (leave a pole, go around, and go back in the other pole), but the lines of force pass through air around the magnet. They'd rather not do that if they have a choice. They'd rather pass through something that will "conduct" the magnetic lines of force. Like a paper clip. Or a tack. Or a lot of them. Iron filings will work, too. Any ferromagnetic material. Ferromagnetic materials that the magnet acts on will "get into the lines of force" if those materials (tacks, paper clips or whatever) can move. That's why you see the "arrangements" of materials that the magnet has picked up. That's why the materials hang around at the poles (the ends) of the magnet. They want to get into the magnetic flux lines, and want to get into as many as they can.

Answer 2

The magnetic field lines are closer together.