Electromagnets and spinning objects

In summary: One is at the top of the big hollow cylinder, and the other is at the bottom of the cylinder. So the whole assembly sees a uniform magnetic field all the way around. You could do the same with just one magnet at the top and bottom, but having the middle magnet helps to keep everything aligned so there's less chance for misalignment.So basically, you would have a floating object with no friction between parts that is kept in place by strong magnetic fields. To spin it, you would need even stronger magnetic fields.
  • #1
D9 XTC
30
0
Okay, so let's say there is an object with a shaft connected to it. The shaft rotationally spins the object.

On the top and bottom of the object are N magnetic fields. Not touching the object or shaft are magnets attached to a solid surface with N fields. Those are within distance to act on the objects magnetic fields that are N fields as well.

Basically, the object is floating (and kept in place by mono fields on the top and bottom) and can be spun.

My question: if the magnetic fields were just strong enough to make the object float (not a very strong field) would it take as much or more energy to spin the same setup except with extremely strong magnetic fields? It seems to me that since there is no friction between parts then even a crushing strong field would be just as easy to spin...
 
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  • #2
D9 XTC said:
Okay, so let's say there is an object with a shaft connected to it. The shaft rotationally spins the object.

On the top and bottom of the object are N magnetic fields. Not touching the object or shaft are magnets attached to a solid surface with N fields. Those are within distance to act on the objects magnetic fields that are N fields as well.

Basically, the object is floating (and kept in place by mono fields on the top and bottom) and can be spun.

My question: if the magnetic fields were just strong enough to make the object float (not a very strong field) would it take as much or more energy to spin the same setup except with extremely strong magnetic fields? It seems to me that since there is no friction between parts then even a crushing strong field would be just as easy to spin...

Could you post a sketch of the setup your are asking about? Thanks.
 
  • #3
Hmm the drawing is done and the picture is on my mobile... I don't see a post picture option though. I tried getting out of the mobile version of this site but it redirects back to the mobile site.
 
  • #4
[URL]http://www.flickr.com/photos/57509695@N07/5655695264/[/URL]

Hope this works... did it all from the mobile...
 
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  • #5
http://www.flickr.com/photos/57509695@N07/5655695264/" [Broken]

Maybe this will work if the other didn't because it can't tell.
 
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  • #6
Ah, got it. BTW, you would probably have N-S magnets on your rotating part (all magnets have N and S ends, and you haven't shown where the S ends are anywhere). But that's not a fundamental part of your question. You can still arrange the outside fixed magnets to all repel the rotating magnetic assembly so it floats against the force of gravity.

I think the main variation when you increase the strenght of the magnets will be that you will get higher eddy currents in the magnetic metal pieces themselves, which will increase the drag on the rotating assembly. If you could make each magnetic assembly out of a hollow cylinder the same radius as the rotating piece, then you might be able to have magnetic force without a changing magnetic field during the rotation, so you wouldn't have any eddy current losses.

This is more of a Physics question rather than EE, so I may move it here in a bit to one of the Physics sub-forums here...
 
  • #7
I think I somewhat understand what you're saying about the hollow cylinder. I'm not sure what eddy currents are... do those only affect electromagnets or do this also affect permanent magnets?
 
  • #8
D9 XTC said:
I think I somewhat understand what you're saying about the hollow cylinder. I'm not sure what eddy currents are... do those only affect electromagnets or do this also affect permanent magnets?

Here is an intro to eddy currents:

http://en.wikipedia.org/wiki/Eddy_currents

Whenever you have a changing magnetic field through a conducting loop (like with wire in a transformer, or just the solid metal of a magnet or other conducting object), a current is generated that itself generates a magnetic field that is in the direction to oppose the original magnetic field. This is what generates the "back EMF" in transformer action, and what is used in eddy current braking systems.

So when your drawing shows individual solid cylindrical magnets, as the rotor spins, the magnetic fields are going to be changing as the magnets align and mis-align during different parts of the rotation. If you could make the magnets always "see" the same magnetic field, then I don't think you'd have eddy current issues that will be generating drag.

So I think one way to do that would be to use a full hollow cylinder for the rotor magnet, instead of individual solid cylinders. The outer radius of the big hollow cylinder matches the outer radius of your rotor, and the inner radius is something like half of that. The magnet is magnetized vertically, as your picture is drawn now.

And opposing that rotating hollow cylinder magnet are two fixed, similar-shaped magnets, one below the rotor and one above. You line up the N-S faces of the two outer magnets to give you repulsion from both to the rotor magnet in the middle.
 

1. What is an electromagnet?

An electromagnet is a type of magnet that is created by passing an electric current through a wire coil. This creates a magnetic field around the coil, making it act like a magnet.

2. How does an electromagnet work?

An electromagnet works by using the principle of electromagnetism. When an electric current flows through a wire, it creates a magnetic field around the wire. By coiling the wire, the magnetic field is concentrated, making the electromagnet stronger.

3. What is the difference between an electromagnet and a permanent magnet?

The main difference between an electromagnet and a permanent magnet is that an electromagnet can be turned on and off by controlling the flow of electricity, while a permanent magnet always has a magnetic field. Additionally, the strength of an electromagnet can be adjusted by changing the amount of electric current, while the strength of a permanent magnet is fixed.

4. Can an electromagnet be used to make objects spin?

Yes, an electromagnet can be used to make objects spin. By placing a spinning object, such as a top or a coil of wire, in the magnetic field of an electromagnet, the magnetic force can cause the object to rotate. This is the principle behind electric motors.

5. Are there any real-world applications of electromagnets and spinning objects?

Yes, there are many real-world applications of electromagnets and spinning objects. Some examples include electric motors, generators, MRI machines, and particle accelerators. Electromagnets are also used in everyday objects such as doorbells, speakers, and hard drives.

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