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Let's say I have two electromagnets and they are resting on a flat surface. For simplicity, let's just say they won't be lifted from the surface. Their size or current doesn't matter. They are not touching, but they are some distance apart.

Would there be a way to set the current on each magnet, relative to the other, such that it would be hard to move either magnet closer or further away from the other? For example, it would be easy to make one magnet move in a circle around the other. but not in a line toward or away from the other.

Does this make sense, and if so, is this physically possible? If it's not possible, would it be possible to use an outside force to accomplish this?

Marty
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  • See https://en.wikipedia.org/wiki/Magnetic_levitation – mmesser314 Jan 19 '18 at 04:41
  • You can just use one electromagnet and use a chunk of iron for the other one. You need some way to sense the distance between the two so you can use that to control the current in the electromagnet. It's an undergraduate electronics project. – Ben51 Jan 19 '18 at 04:48
  • @Ben51 Cool! So I'm not far off then in my thinking. Is there something specific you can point me to read? I'd like to put together a project like this. – Marty Jan 19 '18 at 04:50
  • This sort of thing: http://www.electroschematics.com/6306/magnetic-levitation-circuit/ It would be a bit trickier horizontally as you've described, maybe, but you could work it out. – Ben51 Jan 19 '18 at 04:51
  • Is there an example that doesn't include gravity? I'm not trying to achieve levitation, just holding two objects at a set distance from each other on a flat surface. – Marty Jan 19 '18 at 04:53
  • I guess you would need two electromagnets after all, without gravity, because you need to be able to achieve a repulsive force. Otherwise, I don't see anything fundamentally different about the horizontal case. – Ben51 Jan 19 '18 at 04:57
  • Makes sense. I wasn't sure if I was totally off base or not, so I'll start looking into it. Thanks – Marty Jan 19 '18 at 04:59
  • An electromagnet and a permanent magnet (kept from rotating) works equally well. The horizontal case would be significantly harder, though, since the inductance of an electromagnet makes it difficult to change the current quickly enough to change between attraction and repulsion. – Chris Jan 19 '18 at 06:06
  • @Chris Can you elaborate? When you say "quickly enough," what is a realistic time interval between changes in current, such that they would switch between attraction and repulsion? – Marty Jan 19 '18 at 18:26

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