Uniform magnetic field question (video preferred)

Not sure what you are asking to see. I've seen how a magnetic field can be visualized using iron filings but that doesn't seem to be what you are looking for. I also don't understand why an iron cube, if placed in the center would want to slide anywhere. I would think it would just stick where you put it. There are a number of styles of magnetic plates. Some have just two poles and others are cellular in nature with many small magnetic poles. I think you need to be a little more specific.

Okay, here is a video that shows that iron is slightly less attracted in the region discussed above (the middle of the bar magnet). Thus, meaning that, near the ends, where the field lines converge, it is there where the stronger attractive force exists for attracting iron...



He shows, at about 17 seconds into the video up until about 40 seconds, that the iron is best attracted at the ends.

What I am wondering is, is this also true for plate magnets where one plate functions as the north pole, while the other plate functions as the south (creating a uniform field between). If such a bearing is placed out in the middle of one of the plates somewhere, is it less attracted there than it would be near the edge? (Flux lines diverging or converging at the edge a bit) In other words, is it this flux line convergence that is a contributing part of the iron's attraction?

Again, I had a video showing such a pair of plate magnets separated by about 15 cm. And the person who shot the video had sprinkled iron filings into the region between somehow (that was not shown, only the aftermath). The filings had clumped near the edge, but that may be due to the edge being the first place where magnetism appeared.

With regard to iron, I think the basic rules on attraction are based upon flux-line density and NOT divergence/convergence. In other words, where ever the flux lines are more closely packed together (even if parallel), you get a stronger magnetic attraction?

So, if that's true, and it really has nothing to do with the fact that the flux lines are converging or diverging (it is, instead, based solely upon density of line population) then, in a parallel plate arrangement of two poles of a magnetic system, the attraction of iron to whatever side the iron is closest, is based on the lines of flux being packed together close enough to make the strength necessary to attract the iron, and not because the lines need to be converging or diverging (as stated, they could even be parallel).

So, I think my question can best be stated as, "do parallel lines of magnetic flux, tightly packed together, create magnetic attraction, OR do the lines of magnetic flux need to be converging/diverging to create attraction of iron?"

Also, if close parallel lines cause attraction, would lines packed together even closer (near by) make the iron ball move toward the more densely packed lines?

Thanks for the video! Cool stuff!

Okay. So, parallel "lines" of flux, packed tightly together attract an iron ball and will likely hold an iron ball in place (as long as there are no other flux lines nearby that are even more tightly packed)

But, I'm guessing that if an iron ball is subjected to such a large set of tightly-packed magnetic flux "lines" as this and it turns out that these parallel lines of flux fail to attract the iron, then that might be evidence that the lines of flux actually need to converge instead? (in order to attract?). Or, it is absolutely certain that densely packed parallel lines of magnetic flux (uniform field) readily attracts iron?, (unlike the middle area of the bar magnet seen earlier, which had neither converging lines nor parallel lines of magnetic flux).

Sorry for so much chatter on the topic, BTW. I'm trying to be clear on what configuration of lines best predicts magnetic attraction. I'm thinking it is solely density and has nothing to do with their being parallel, converging, or diverging. Any stronger attractiveness seen at the end of a bar magnet, where the flux lines happen to converge, is merely a demonstration of increasing DENSITY of the field lines, and not some mysterious requirement for the lines to converge. That's basically sound reasoning, isn't it?

I don't have a thought or feeling one way or the other about the so called lines. I have no other way to talk about them, and they are commonly referred to as lines. Do you feel I see them as actual lines? I see it more as a kind of force vector field. Except, magnitude is shown in how tightly clustered the vectors are, not their length. Something like that, let's say. Is it because I was trying to determine if the direction that the force vectors were pointing had something to do with their strength?

Back to using the concept of force vector lines as a means to show field strength, using how near the vectors are with one another to show strength and not their length, or, apparently, direction as we've just found (just to be clear): it is interesting to see that in some diagrams of a bar magnet the lines are closest together at the center of mass (inside the center of the bar) and, yet, the metal ball falls off when near the center of the bar, arguably in very close proximity to high field strength (as seen 17 seconds into the second video from top, above) it falls apparently because the direction of the vector is pointing perpendicular to the iron ball.

Yet, as we've agreed, direction of these vectors is not supposed to be a contributing factor to field strength? As we further agreed, parallel force vectors that are more tightly packed together, near an iron object already trapped in more loosely packed "lines", are going to pull the iron ball away from where it is currently attracted. So, proximity can be a factor (Again, using video 2, about 17 seconds in, we see this something like this principle in action when the ball rolls toward one end) however, sometimes merely being in close proximity to densely packed field lines is not enough. After all, the ball also falls off the bar, even in arguably close proximity to high field strength, at the bar's center.

Okay. So, in a situation where there is a nearby, greater-density of field that causes an iron object to move toward that denser field when allowed to do so (say in some case where the object is already in contact with one of the poles for having been placed there, but, when let go of, it slides over to the more densely packed area of field lines), this happens because there is not a uniformly-distributed group of field lines passing through the ferrous object, but, instead, some slightly denser grouping of lines favoring the side that the object slides over towards, once released (and is, as you say, already inside the object).

In the case of video 2, where the bearing is nudged away from one of the poles so that when it is released, it rolls back toward the polar end, this is likely due to the fact that there is a sort of tidal force (uneven grouping of lines) occurring within the bearing.

In other words, as you say, the lines have to pass through the object in question. So, if a bearing, placed on a flat magnetic sheet, such sheet supposedly part of a system making a uniform field, and the bearing is released wherein we find it rolls along the sheet, settling in another area, that sheet had to actually contain a non-uniform magnetic field, and some of the denser set of field lines had to have passed through the ferrous object (the denser area of lines couldn't have been merely nearby, but some of the uneven distribution of parallel lines had to be inside the ball too, even if hard to tell)

I think that follows what you've said.

EDIT:

So, to the point: Would you suppose that an iron ball bearing could be used to verify that a supposedly uniform magnetic field is actually uniform? (a field like that found between large magnetic plates, for instance)

Two things I wonder the app could answer: One, if it is true that a ball bearing rolling helps give some indication of any imbalance found within the magnetic field, and if iron re-organizes itself into a magnet when under the influence of a magnet, how does the iron roll if it is aligned into a rigid north/south pole type magnet? Does the alignment constantly change as it rolls?

Also, it was stated earlier that filings attach themselves onto a magnet such that they accumulate into a larger system of magnets... If this is so, is there a limit? I don't think I'd expect dropping a single rare-earth magnet into a Olympic sized pool of iron filings would result in an Olympic sized pool magnet. Isn't it possible that the iron filings merely attach to the existing field, not really changing the overall size and complexity of the original magnetic field?

How close to the magnet? Such that it encapsulates just the original field volume exactly? If so, this sounds more like it just attaching to the original field, not creating a 'super magnet'.

(you just lost me there a bit. not trying to argue against what you say, because I realize it is more likely correct than not, but I don't really see how what you've written describes a super magnet)

GTCGreg, I want to take a moment to thank you again! You've added a new dimension to my investigation on this topic and I intend to further research everything you've said, to include the "super magnet" concepts!

I feel it is rare to find someone who is willing to field so many questions. Usually, a brilliant person such as yourself comes to an early conclusion that it is not their job to educate the under-educated and further decides that the person asking so many questions is just lazy, beyond help, stupid whathaveyou. So often this situation breaks down into a slam against the person who is lost. But, you never did that! You have wonderfully and briefly described what are arguably difficult concepts. I really appreciate it! I may return here again once I have more data!