# Can a particle revolve around a magnet

1. Jul 5, 2010

### sabdulhaq

My question is that can we make a metallic particle revolve around a magnet ,like planets revovle around a star or electron around a nucleus.....e.g can iron grainy particles revolve around a powerful magnet ?

2. Jul 5, 2010

### Born2bwire

Around a magnet.... be a tall order. But yeah, you could. A moving charged particle experiences a force from a magnetic field. The direction of the force is normal to both the particle's velocity and the magnetic field. So if we have a uniform magnetic field that is normal to the direction of a charge's velocity, the charge will move in a circular orbit. The radius of the orbit depends on the magnitude of the charge, the velocity and magnetic field strength. With a bar magnet, the field will vary in both direction and strength in space. However, the field should be more or less cylindrically symmetric along the magnet's axis (we could make the magnet a rod too). So as long as you choose a plane where the magnet's fields are more or less perpendicular, you can get a charge to orbit since the field strength should not vary over a perfectly circular orbit. Course you would have to find the perfect balance in properties and this is probably easier said than done since any loss in the kinetic energy of the particle would upset the orbit.

3. Jul 5, 2010

### AJ Bentley

Actually, thinking about it, this is exactly what we do in a cyclotron.

You don't need anything fancy, an ordinary 'horseshoe' magnet would do - the type where if looks like a 'C' with the two pole- pieces facing each other.

If you fire a charged particle into that gap at the right speed at will go round in a circle and keep doing that.

4. Jul 5, 2010

### pallidin

Not for very long at all.
Gravity is, in this context, very weak, which in part allows a mass body to revolve around a greater mass object for some time.
A magnet can be MUCH more powerful with respect to pulling forces at short distances as you allude to. The iron particles will quickly "de-orbit" and stick to the magnet.

5. Jul 5, 2010

### Sobeita

If you used a straight bar magnet, I think that might be better, because the other pole would be way out of the way. Then you could calculate the exact distance where gravity and magnetism cancel each other out, find a speed that forms an orbit, and 'throw' fine iron powder specks in. (I'm picturing a big magnet with the attractive side pointing down, then below it a few inches, a little asteroid belt of magnetized iron.) Maybe in a vacuum this could be perfected so that they stay at that height and don't spiral up/in... oh, and avoiding colliding the particles with each other would help.

6. Jul 5, 2010

### ZapperZ

Staff Emeritus
I think the OP's question involves a "metallic particle", such as iron filings, etc. In other words, not a charged particle.

Zz.

7. Jul 5, 2010

### Sobeita

That may be true, but I think the specifics were just to help us understand the question a bit better. The question itself was to ask whether or not orbit was possible in a magnetic field or if it was somehow just confined to gravitation. That's how I interpreted it, in any case. I've just gotten back from a long flight, I'm probably not reading stuff well.

So, charged or not, is it possible the way I described it, or with other variations? Could you make a rigidly fixed bar magnet hold up a rotating belt of iron filings in a vacuum?

8. Jul 5, 2010

### Born2bwire

He could always charge the particle. Though I don't think that this is a practical method.

9. Jul 5, 2010

### pallidin

Not in the sense of perpetual motion, if that's what your after.

10. Apr 22, 2011

### sabdulhaq

It is not neccessary that paritcle to be charged because magnets dont work on charged particles but they attract mettalllic partilces like iron fillings.