# Monopole magnetic material

ZapperZ
Staff Emeritus
A magnetic monopole field would resemble the electric field pattern of a point charge. If a closed volume included an isolated magnetic monopole, the divergence of B is non-zero. If an enclosed volume is located in very close proximity to the mag monopole but does not enclose the monopole, the div B = 0. In this volume, the B field lines exit the monopole and enter the volume, pass through, and exit the enclosed volume.

A bar magnet, when viewed from a small enclosed volume very close to a pole, but not enclosing the pole is now examined. Here, div B = 0. Also, the B lines emanate from the pole of the bar magnet, pass through the enclosure, exit the enclosure, then eventually wrap around to the opposite pole. But if the enclosed volume is small enough, and very close to the pole of the bar magnet, the field lines in the enclosed volume appear very similar to that of the first case above. The wrapping around of B is far away from the enclosed volume, so that there is a similarity.

However, under no circumstances does this produce a non-zero divergence of B. This analogy is quite limited. If you're looking for a B field with non-zero divergence, then this analogy does not produce that.

Have I explained myself well? BR.

Claude

You have explained it, but it is extremely puzzling how you are able to convinced yourself of what I've highlighted in bold. How are you able to show that in that small volume, the field resembles that of a source charge? How small is "small enough"? Can you show a mathematical derivation that this is the case?

Zz.

See this image:

How can you ever get a similar magnetic field without actually having a monopole? Even if you look very close to a normal bar magnet so the field lines are essentially straight and you don't see them 'wrapping around', there is still the case that there are field lines will enter the 'volume' you are looking at, and field lines that will exit the volume. In the case of a monopole (as in the picture) there are only exiting or entering fields.
(By exiting and entering I mean regarding the 'direction of the arrow', I know it's not the right word but I don't know how to explain it further...)

See this image:

How can you ever get a similar magnetic field without actually having a monopole? Even if you look very close to a normal bar magnet so the field lines are essentially straight and you don't see them 'wrapping around', there is still the case that there are field lines will enter the 'volume' you are looking at, and field lines that will exit the volume. In the case of a monopole (as in the picture) there are only exiting or entering fields.
(By exiting and entering I mean regarding the 'direction of the arrow', I know it's not the right word but I don't know how to explain it further...)

I've already stated what you've pictorially depicted. Good pic by the way. In the pic above, if a small volume encloses a monopole, then div B is non-zero. This cannot be duplicated with a bar magnet. The point I was making is that you can never get a non-zero divergence until a monopole is discovered. For now that hasn't happened.

My bar magnet analogy was mentioned just to show that the field line pattern very close to one of the poles resembles a pattern emanating from a monopole. The condition I stated was that the small volume is near the pole so that the wrap around is outside the said volume. The field lines resemble those if a monopole were present OUTSIDE but very near the volume. With a true monopole there is no wrap around at any distance. With my example, there is a wrap around, but not "seen" inside a volume in close proximity with small volume.

I've also stated explicitly that " div B = 0 " is a law we cannot get around ever. My analogy is very limited, and I do not claim that a region in space very close to a pole on a bar magnet is exactly like a monopole in the true sense, as it is certainly not.

We seem to have universal agreement. We all know that div B = 0, in all cases with real magnets regardless of how close to the pole, regardless of how small the volume.

We agree. No need for debate.

Claude

There is a purpose for monopoles or should I say virtual monopoles. I have fashioned a (continuous shape) whereby the two poles are far enough apart to resemble the afore mentioned description by Cabraham. What its' use will be is still in R+D. I does work as expected though, meaning you can shape an H/B field to suit a purpose, mine being flight.

I inadvertently fell into this, constructing an exterior magnetic field as a sensor or receptor of H/B field when I noticed the properties of the field is not the property of the magnet but instead its' a property of the poles. From there it was much easer to understand the behavior of the field relative to its' surroundings and how it can be shaped.

Thanks again for the input from Zex and Berkeman in the Electrical Engineering Forum

My apologies for being vague.

I have constructed an object that indicates that there is only one pole around its' entire exterior, as well as, at four distinct points the flux is very strong. Each point/spot is 120 degrees off-set in relation to each of the other four intense flux spots. I really don't see, that it's all that complicated. I know what my intentions are for this is but what would anyone else do with this?

OK, whatever. I would be willing to bet that you did not actually construct this object apart from drawings on paper that you think works.

And those polar field lines some think are straight are not straight at all.
They eventually curve to the opposite pole.

The reason most iron-filing set-ups appear to show a polar straight line is that the magnetic force at that point is too weak to align the relatively massive iron-filings into a curve.

Well I tried it. I took a 300mm Iron rod and a N42 nib magnet, starting in the center of the rod and switching to the other side, again starting from the center after each stroke. I then brought it proximity to a compass and indeed the north end of the needle pointed to the end of either side of the rod. I also noticed that the south end of the needle pointed to the center of the rod as I was passing it. So, what you have is not a monopole it just has the same pole on each end and the opposite pole in the middle.

about 2nd solution, when you conected to magneteic with north-north, and South - south , infact, you have one magnetic which is weaker than both of first mgnetic because, their magnetic fields destroy each other....