Behaviour of iron in magnetic field

1. Feb 13, 2006

KKK

Assume that iron dust is mixed with non magnetic dust or powder and it requires separation.
How would the iron dust behave if the material containing the iron dust is allowed to fall through a magnetic field zone created by placing electromagnets in an array so that the magnetic zone is about 600 mm wide (across the flow), 100 mm thick (flow thickness) and 1000 mm deep (along the flow). While free falling through this zone the iron particles should get attracted to the electromagnet poles. The free fall would allow the iron dust particles to move freely towards the poles.
Do you think that this will happen?
What do think should be the strength of the magnetic field?
Would the iron behave as if it is in any other force field, say, like gravity, where it would get attracted to the nearest mass?

2. Feb 13, 2006

Astronuc

Staff Emeritus
One needs to show one's work or thoughts before asking for help.

It would appear the problem is one of magnetic separation.

3. Feb 13, 2006

Mk

It depends on each particle's volume and weight. If the gravitational field is strong enough, the particles would just fall through. If the magnetic field was strong enough, well of course the particles would stick to the magnetic field!

4. Feb 14, 2006

KKK

Yes. The iron being micronic in size its volume is also very small and so is the mass. What I thought was that like the equation G.ma.m2/d^2 for Gravitation, magnetic equation would also apply. However I am seeking the views of others whether this would be true in entirety.

5. Feb 14, 2006

KKK

I respect your views about showing work and then asking help. This case happens to be beyond simple magnetic separation due to the fineness of the iron dust. I thought it worthwhile to contact others who would know more in the field and so their opinion would be valuable. If you have experienced the behaviour of iron dust falling down through a block shaped magnetic field, it what I am seeking. There are two forces acting, gravity downward and magnetism across the gravity. Would the iron dust "float" to the nearest magnetic pole. Please suggest a book or Internet site giving more information on it.

6. Feb 14, 2006

Mk

The dust would fall in a curve towards the poles. I'm seeing something like a horseshoe-shaped electromagnet, with the poles like

_________.............__________
_________}..........{__________

^
And the dust falling in between (without dots)

It would fall in a curve because, well gravity is pulling downward, and magnetism is pulling left or right.

7. Feb 14, 2006

KKK

Thank you Mk. I thought similarly. I am at a task to determine how the curve of fall can be designed so that the iron gets away from the fall of the non magnetic material. The "Block Magnetic Field" I thought could be created by puttting the N poles on one side and S poles opposite, so that the magnetic field lines would be straight from N poles to S poles and would act as a magnetic filter. Would I be right in thinking so? Next would be how to design the strength of the field. Sidewise acceleration could be imparted by the magnetic filed. The task would be to determine "how much stronger". Do you have any ideas or references?

Last edited by a moderator: Feb 14, 2006
8. Feb 14, 2006

pinestone

From a practical point of view, the gap between the poles would get smaller. Particles that get attracted to either poles become magnetized and extend the electromagnetic field closer to the center. These magnetized particles attract more particles, and they become magnetized and so on...I think you would end up with a conical.

9. Feb 16, 2006

KKK

"The dust would fall in a curve towards the poles. I'm seeing something like a horseshoe-shaped electromagnet, with the poles like

_________.............__________
_________}..........{__________

^
And the dust falling in between (without dots)

It would fall in a curve because, well gravity is pulling downward, and magnetism is pulling left or right."

Now, consider that the magnet poles are in the shape of two plates 600 mm wide and 1000 mm deep, facing each other about 100 mm apart.
If sufficient magnetic pole strength is provided to the two plates (one plate as N pole and other as S pole) a block field should form between the two plates.
The iron particles should get attracted to one of the poles if they are made to fall between the two poles (and through the block magnetic field). The curve of fall should make the iron particles to take them to one of the poles and out of the flow of the remaining non magnetic material.
This should cause the iron particles to come out the non magnetic material.
Is this thinking correct?

10. Feb 16, 2006

Astronuc

Staff Emeritus
11. Feb 23, 2006

KKK

Forec on iron in magnetic field

Conventional / commercial organisations do not appear to get involved in such an abstract problem. I have already approached the suggested site but I learned there that such a system would not work, which I think is not correct, it should work.

The iron particle would be expected to move towards the nearest magnetic pole.

I have attempted to calculate the force exerted on an iron particle having a diameter of 20 microns. I assumed the following relation -

F = Mu*(NI)^2*A / 2*L^2
with usual convetions in SI units
Mu=4*pi*10e-7
L= distance between the pole face and iron particle.
N=number of Turns
I=current in amps

for starters, I assumed Ampere turns NI = 350 turns x 5 amps.

I landed with a force of 32 N. Which appears to be too high for a particle of mass of 3.288E-11 kg. This would give the particle nearly impossible acceleration, which does not appear to be right.

I am trying to find whether something is wrong with the use of the relation above. May be the value assumed by me was too high. I have attempted the calculation with an electromagnet and I shall try that out with a permanent magnet.

Do have any hints to give?

Last edited by a moderator: Feb 23, 2006