Magnet Myths and Misconceptions

[Qwert]

Magnetic field lines would be quite useful element in calculations. Do you know guys a formula which includes them? Especially supported by scientists who have them in their suggestions.

[vineet_kiran]

  To get a permanent magnet motor to run it is very simple.  Polarize a permanent magnet so that it creates a magnetic field that duplicates the magnetic field of a copper wire conducting dc current.   If you can youve got a winner.   Replace conductor in below picture with said dynamic permanent magnetic thing and watch her spin for 400 years,

Looks very simple.  Can it be like this? (see the attachment)

[MileHigh]

  I first figured out how current through a static magnetic field forced the current carrying metal to move by reading a very old book published around 1901 dealing with electromagnetism.  It was a practical guide for electric motor technicians and engineers.  Below is a picture I drew up fast to duplicate the much better diagram from the book.  The magnetic field is like water blowing across the ocean surface.  In the diagram this is from left to right.   The conductor current is flowing into the page.   (could be out long time since I did any right-hand left hand stuff)   A circular flow of magnetic current is created as indicated by the arrow around the conductor surface.   The rotating current increases the total magnetic pressure on top of the conductor whereas it decreases the magnetic pressure below the conductor.  Therefore the conductor moves from the top of the page to the bottom.  Something like an airplane wing or a sail.  The wind because of it's viscosity has to travel faster around the bulge in the wing or sail.  This decreases the pressure.   The lower side of the wing or the more or less flat side of the sail allows the wind to flow unimpeded and at a velocity less than the air traveling the bulge.  The split stream converges at the trailing edge of the wing or sail at the same velocity as the bulk flow of air relavent to the craft.  Anyway the pressure is greater under the wing than it is on top and this lifts the craft up as the ambient pressure continually tries to fill the partial vacuum created by the fast moving air. 

Sparks:

Here is a clip that shows the force between two wires carrying electric current. One wire is modeled as the source of the external magnetic field and the other wire is modeled as the wire that experiences the force, so it is identical to your example.  The actual example starts in the middle of the clip.  I also attached the formula of as a screen capture.

The fundamental concept that it's all based on is that the current vector (magnitude and direction) of the wire that experiences a force interacts with the magnetic field vector (magnitude and direction) of the external magnetic field.   The force on the wire is proportional to the cross product of the current vector and the external magnetic field vector.

This is just one step above mastering magnets and magnetic fields.  What are vectors?  What's a dot product?  What's a cross product?  How does this relate to the right-hand rule?  If you are building motors and you are serious you have to master these concepts.

The explanation starts in the middle of the clip:

https://www.youtube.com/watch?v=NfDQFtY1n8E&list=UU6x7DywfEqLg-3Cg_JnyTlg

MileHigh

[MileHigh]

Well, it's like this.

When we construct a model of a phenomenon, we may, or, may not, happen to hit upon  the exactly right visualization that will coincide with what we see when we look with clairvoyant vision upon that phenomenon and see it in its intrinsic real reality exactly like God sees it.

So, if the Faraday model of field lines proves to work out to give the theorists and the engineers and you and me and all the rest of us good and useful answers, then we, still in our non-clairvoyant bewildered mere human condition, have no good basis to say that the field line model is not real. It may be real or it may be fantasy, but if it works, then you don't have any case for claiming that it is not real.

And likewise, I do not have a conclusive case for saying that it is real because I am just so sure that that is how God sees it.

You cannot prove one way or the other just like I cannot prove one way or the other.

Perhaps you disagree.....


G'day mate
CANGAS 86

Cangas:

I disagree strongly.  Hopefully this new example will swat this nonsensical belief in literal "lines" or "threads" of magnetic field.  There are NO LINES.  The lines are there ONLY to help you visualize the strength and direction of the magnetic field, and that's all.

Look at the attached diagram.  Do you think that there are real "lines" in the air?  What is your common sense telling you?  Now apply that common sense to magnetic fields.

You cannot prove one way or the other just like I cannot prove one way or the other.

You can't prove that there aren't pink elephants floating over the sky in the center of Greenland either, but you can use your common sense and not let yourself get led down a garden path because you see lines used as a visual aid in diagrams.

MileHigh

[MileHigh]

To be very clear, I have got a simple question :

When you pass a DC through a conductor, electrons flow or move like 'Newton balls' and a magnetic field is created around the conductor conforming to right hand thumb rule.   

Instead of passing a DC through the conductor, fully charge the conductor with electrons and move the conductor itself physically by applying mechanical force,  will the conductor create a magnetic field around it?   YES or NO.

If you say 'YES', it will have its own implications.  If you say 'NO',  then you will be conforming that electric charges moving under the influence of electric potential (voltage) only will produce magnetic fields. 

If you are not interested, please don't respond.

Newton II:

When you pass DC current through a conductor there is no "Newton balls" phenomenon taking place.  To me "Newton balls" implies electrons enter one end of a conductor and "push" on adjacent electrons to form a chain reaction where electrons at the opposite end of the conductor get "pushed out."  That is not happening.

We are going to assume a real-world conductor with a very low resistance.  There will be a very low level electric field in this conductor such that there is a very low voltage drop from one end of the conductor to the other.  This low level electric field is what makes the electrons move.  Each individual electron is influenced by the electric field and thus they all move in the same direction at the same time.

Instead of passing a DC through the conductor, fully charge the conductor with electrons and move the conductor itself physically by applying mechanical force,  will the conductor create a magnetic field around it?   YES or NO.

NO because you can't "charge" the conductor because you are implying this conductor forms part of a circuit.  There is no net charge on a conductor that forms part of an electrical circuit.

What perhaps you are actually thinking is if you had an isolated conductor and you charged it up with static electricity then would it create a magnetic field if you then moved it by applying mechanical force to it.  In this situation it's just a variation on a moving point charge.  Instead of a moving point charge you are talking about a moving long thin cylinder of charge. That would create a magnetic field if you moved it.

MileHigh