Magnet Myths and Misconceptions

[TinselKoala]

Can you provide some reference for this idea of momentum flowing along magnetic field lines?


Anyhow, here's the small homopolar motor I promised. What is making it turn? What is being pushed against, and how?

http://www.youtube.com/watch?v=wFMq1Cvtg1s

[bboj]

Argh. Charge, motion, field: one thing. One.

What is moving? Charge. What is the smallest chunk of charge? The Unit Charge. Where are these charge chunks? The Negative one is carried by and is inseparable from the electron. The positive one is carried by the proton, and also the positron (the electron's antiparticle). Normally we never actually see those positive charge carrying particles because the proton is buried deep within the nucleus of atoms and the positron is only made in energetic reactions and doesn't stick around very long. So the positive charges we see, like on the top of a positive Van De Graaff machine, are actually "holes"... deficiencies in electrons, places where electrons should be to make everything neutral, but for some reason they aren't there.
OK, now in wires carrying current, you can think of the charge moving fast through the "electron gas" of conduction band electrons, like the momentum moves through a Newton's Balls system, or if it is easier you can think of the electrons themselves flowing along in the wire. Either way, the current (moving charge) is pushed along by the fact that at one end of the wire there is more negative charge than at the other. This of course also means that there is more _positive charge_ at the other end of the wire-- holes where electrons should be.
The reason metals don't flow and collapse from all this electron charge moving around is because there are a bloody _lot_ of electrons, a Coulomb is a huge number of them, and even with currents of kilo or megaAmperes we are still only moving a tiny fraction of the electrons in the wire.
Now, when you move a charge you get an associated magnetic field around it. The field has geometry and strength that is determined by the path and speed of the moving charge. You can think of it like the bow wave ahead of a moving boat. Each moving charge has its tiny "bow wave" of a magnetic field circling around the path of  motion. (But what acts as the "water" in this analogy? That's a very deep question.) But there are many many many charges moving in even the smallest currents. So if you were really tiny and could watch your wire, and a tiny single charge came by, being pushed from behind by MH's "field" or by charge pressure from the charges behind it (same thing) you would see a bump on your field detector as the charge came by. So a DC current--- a single moving charge -- generates a dynamic, changing field at your fixed location as the charge moves past. But there are many many many charges flowing in the tiniest real DC current, so you see what looks like a strong, static field at your measurement point, as the charges flow past so many and so fast your finest instrument can't tell them from a continuous flow of homogeneous fluid.

Now we do know why, or rather how, a boat makes a bow wave. You can't really move through the water without making one and the faster you go the bigger the wave. Charges make magnetic fields as they move relative to the observer. If the observer moves along with the charge... you don't see the magnetic field (because the field just describes how a thing will move and you are already moving that way) but you do see the electric field from the charge which isn't moving with respect to you. Now that duality of electric and magnetic fields, discriminated only by relative motion, is, to me, a grand mystery of the Universe. "Why" does that happen? Well, some people believe that that question can be answered in a meaningful way, and that's why they go out and build particle accelerators and learn complex mathematics. I just look around in awe, myself, and give thanks that things are the way they are. Maybe they could be different... but I doubt it.


eta: The electron's charge cannot be removed from it, but an electron isn't "just" a packet of the Unit Negative charge. It has mass and spin angular momentum as well. What is really weird is that it does not appear to have a "size"... it is considered a point particle, or a probability cloud.

I checked back.
I know what you mean. Thanks

[CANGAS]

Can you provide some reference for this idea of momentum flowing along magnetic field lines?


Anyhow, here's the small homopolar motor I promised. What is making it turn? What is being pushed against, and how?

http://www.youtube.com/watch?v=wFMq1Cvtg1s

Can I provide a reference? If I had a dime for every time I have seen an internet shyster raise this as his defense, his skirt to hide behind.....

Well, you see, actually , Yo hero Tesla did not have a reference to provide all the time, did he?

The best reference for momentum and field lines would be your own physics wisdom and understanding, but you have just been seen to drop the ball and cleverly try to switch the subject so subtlely that nobody has noticed it.

You have evaded the issue momentarily, but I am not lured by any kind of sly trick you might pull out of your cuff. I know a bit about homopolar motors, and it is almost certain that any gimmick you might have to show is one that I have already discovered in my studies.

I do not do Youtube thingys for several reasons. So I have not looked at your Youtube thingy. But, of course, I bow down to the unlimited truth that everything that can be seen on a sleezy Youtube clip MUST be the perfect truth, OK?


CANGAS 89

[TinselKoala]

So that would be a "no" then. And now you are back to being the CANGAS we know and love. I was worried about you there for a moment. When you start to agree with me, I need to go back and check my work very carefully.

[bboj]

Can you provide some reference for this idea of momentum flowing along magnetic field lines?


Anyhow, here's the small homopolar motor I promised. What is making it turn? What is being pushed against, and how?

http://www.youtube.com/watch?v=wFMq1Cvtg1s

I think it pushes against the magnetic field induced in the brush.
The brush is not in contact all the time but is pulsing.