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I know this is a really simplistic question, but I just want to check my assumption. Say you had a cuboid-shaped, permanent magnet, with the north pole on the side facing to the right, and the south pole on the side facing to the left. Am I right that the top, front, bottom and back sides of the cuboid magnet would exert no net magnetic force on a second (semi-big) magnet when you held that second magnet close to any of these four sides? Of course, I realise that there would be a force attracting or repelling the second magnet round the corner if you held it close towards the ends of the big magnet, but am I right that no actual attractive or repulsive force would be emanating from any of the four sides mentioned?

The other thing I was wondering was, if you had a hypothetical magnet that was as small as an electron, and you then held this miniscule magnet against any of the other four sides, am I right that it would experience attractive and repulsive forces from all of them? I think it must, because I know you can think of magnets as being made up of electrons which create microscopic domains inside that magnet, where all the domains are lined up. Therefore, I imagine that there would be sort of cross-sections in slices of the north poles of the domains all lined up and of south poles of the domains all lined up along the entire length of the magnet, meaning that these microscopic poles would cancel out for a large object, but could interfere with a microscopic object as small as they are? Although, if so, then how does this fit in with the way that an actual microscopic electron interacts with a magnet? And, if not, then what was the error in my reasoning, and why?

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  • $\begingroup$ Take a bar magnet, cut it in half. What happens? Now cut it in half again. What happens? $\endgroup$ Aug 18, 2021 at 17:48
  • $\begingroup$ That's an experiment that you can try at home. $\endgroup$ Aug 18, 2021 at 21:08

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I doubt if it's possible to make clear the idea of a force emanating from one face of a magnet. What does have a clear meaning is a magnetic field line: a line whose direction at each point along it is the direction of the magnetic field at that point.

Have you ever used a small compass to plot magnetic field lines due to a bar magnet? If so you'll have discovered that these emerge not just from an end-face of the magnet, but from the sides of the magnet near one end (the North pole end) and return not just to the other end face. The reason is that the magnetic domains are not perfectly parallel inside the magnet, but 'splay out' because of mutual repulsion near the ends.

This answer has addressed only the first paragraph of the question. Regarding the second paragraph, I'd recommend that you start by reading the article on magnetic domains in a well known online encyclopedia! Especially, perhaps, the section on Bitter patterns.

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