Poles of Spherical Magnets

We know that the poles of bar magnets are actually at both ends, and the poles of horseshoe magnets are at both ends. But what about spherical magnets? If one is in the center of the sphere, one is in some part of the surface or on the sphere, it is obviously not tenable, because, in this way, there is no magnetic field around the spherical magnet. If we say that there are two relative points on the sphere, then obviously there can be countless magnetic poles, which is also impossible.

magnetic poles

In fact, the magnetic poles of neodymium sphere magnets in nature are usually at both ends of a certain diameter, such as the NS poles of the earth. Of course, there may be a slight deviation, but it will not be much worse in general. As for artificial spherical magnets, their poles are related to the direction of magnetization during manufacture. There are many kinds of materials for artificial magnets, but no matter which kind of material is made into a certain shape and then magnetized. Therefore, its magnetic pole position is determined by the magnetizing method. When the direction of magnetization is determined, the magnetic poles are at both ends of the sphere diameter in that direction.


We can also think about it through an ideal experiment. If a bar magnet is separated symmetrically from left to right by a straight line from N to S, then a very small piece is cut off on the left side and a very small piece is cut off on the right side at the same time. Then the remaining large N and S poles remain primitive. Repeat the action until the magnet is spherical. At this time, the magnet must still retain the original orientation of N and S poles. That is to say, the magnetic pole of a spherical magnet should be the same as the magnetic field of the earth, in effect, as a long magnet. The magnetic force line emits from the N pole and forms an arc in the outer space, pointing to the S pole. Inside the magnet, the line of force points from the S pole to the N pole.

Similarly, the external magnetic field of a hollow spherical magnet is the same as that of a solid sphere, and the magnetic poles are distributed at opposite poles. In the internal space, it is also a polar magnetic field.

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