Magnet Myths and Misconceptions

[MarkE]

Couple interesting photo's.
The first is a science project my 10 year old son did proving the iron filing experiment found in every textbook is incorrect. The filings align forming lines due to magnetic induction which he showed on a larger scale with short suspended iron wires. It is not a true representation of the magnetic field it is an effect produced by magnetic induction due to the presence of a magnetic field. Magnetic viewing film is simply smaller pieces of iron suspended in a film and ferrofluid even smaller iron particles. The scale of the particles may change however the effect of magnetic induction is the same.

Do you or do you not understand that induction requires a changing magnetic field?  Iron filing experiments are performed with static, unchanging magnetic fields.  Kindly explain the induced field after:  1s, 5s, or 1 minute.  Do the filings align differently in those time frames as the induced electric field diminishes towards zero?

The second picture is a bar magnets field captured using neutron spin, I believe, which is a more true representation of the field in my opinion. The reason for the curvature in my opinion is leakage, take one magnet and the field curls back on itself...the dipole field. Take two magnets together and the main field curls back plus each individual field of each magnet also curls back as flux leakage. Now take millions of dipole fields combined to produce the main field but all produce flux leakage in themselves which forms a field distortion. Obviously flux lines cannot cross because there are no lines in reality and it is a simple effect produced my magnetic induction. However the field can be distorted in the near field which is perfectly acceptable according to the laws we know.


The thing to remember is we know flux leakage occurs and we also know every magnetic field we see is the combined effort of many smaller magnetic fields. So why would we presume flux leakage occurs on one level but not the other?.


AC

No presumption for or against flux leakage is necessary to make correct observations using ordinary static magnets and iron filings.  If you would like to investigate further, go buy one of those nice analog output Hall effect sensors from Allegro Microsystems probe, record, and plot the magnetic field orientation and magnitude around various magnets, permanent and electric.  You will see that the conventional view offered with lowly iron filings is in fact correct.

[tinman]

  You will see that the conventional view offered with lowly iron filings is in fact correct.

The iron filings do not show a correct representation of the magnetic field around a magnet,and the reason for this is because each individual iron filing becomes a tempoary magnet it self when in the presence of a magnetic field. So you are basically surounding your PM with very small PM's when you use iron filings. If you want to know what the actual field looks like around say a rod magnet,you simply put two tennis balls together--this represents the field shape around a rod magnet. The field strength of a magnet is at it's strongest at the center(between the two pole ends),but it is concentrated within the magnetic material,and thus the reason for the zero attraction force around the outside of the center of the magnet. Picture a figure 8,and you have your magnetic field shape.

Oh-by the way-the coriolis effect has nothing to do with this mistical bloch wall,and everything to do with a force that is acting in a direction that is perpendicular to the axis of the rotating mass.

[MarkE]

The iron filings do not show a correct representation of the magnetic field around a magnet,and the reason for this is because each individual iron filing becomes a tempoary magnet it self when in the presence of a magnetic field. So you are basically surounding your PM with very small PM's when you use iron filings. If you want to know what the actual field looks like around say a rod magnet,you simply put two tennis balls together--this represents the field shape around a rod magnet. The field strength of a magnet is at it's strongest at the center(between the two pole ends),but it is concentrated within the magnetic material,and thus the reason for the zero attraction force around the outside of the center of the magnet. Picture a figure 8,and you have your magnetic field shape.

Oh-by the way-the coriolis effect has nothing to do with this mistical bloch wall,and everything to do with a force that is acting in a direction that is perpendicular to the axis of the rotating mass.

Tinman, the fact that iron filings magnetize is exactly why they are a good indicator of the the magnetic field orientation and strength.

If you want to test your hypothesis, then that is easy:  Go purchase an analog Hall effect sensor and probe the field of a dipole magnet or any other magnet shape you care to look at.  Or you have a large dipole, like a long wooden dowel or plastic rod with a winding along its length, then you can just use a compass.  The figure eight idea you promote would cause the compass needle to turn 90 degrees at the dipole center when held off axis.  That does not happen.  Held off axis, the compass will always point most parallel to the dipole closest to the dipole center.

[allcanadian]

@Mark E

Do you or do you not understand that induction requires a
changing magnetic field?  Iron filing experiments are performed
with static, unchanging magnetic fields.  Kindly explain the
induced field after:  1s, 5s, or 1 minute.  Do the filings align differently in
those time frames as the induced electric field diminishes towards zero?

Ah I see the problem you are thinking of Electromagnetic Induction and I am speaking of Magnetic Induction.
Magnetic Induction: 1.The process by which a substance, such as iron or steel becomes magnetized by a magnetic field. The Induced Magnetism is produced by the force of the field radiating from the poles of the magnet.

No presumption for or against flux leakage is necessary to make correct
observations using ordinary static magnets and iron filings.  If you would like
to investigate further, go buy one of those nice analog output Hall effect
sensors from Allegro Microsystems probe, record, and plot the magnetic field
orientation and magnitude around various magnets, permanent and electric.  You
will see that the conventional view offered with lowly iron filings is in fact
correct.

That was what I was using when I made the measurements, an analog hall effect sensor as well as a hall effect sensor array I built as I stated in my prior posts. Your not listening and inferring things which are incorrect. I did not say induction I specifically said "Magnetic Induction" which is a very simple and well know fundamental principal known to most everyone who understands basic physics. A permanent magnet having a magnetic field will induce a magnetic field of opposite polarity in a piece of iron within it's field of influence. The induced magnetic field in the iron is considered as a separate magnetic field in itself and can be measured as such even though it is a function of an external field.
To make my point, I try to avoid superficial observations which tend to confuse even most experts and concentrate on Primary Physics. This is the primary field phenomena such as the Electric, Magnetic and Gravic fields in their most fundamental forms. It avoids all the confusion I am seeing here and concentrates on the most fundamental interactions between the Primary Fields. You need to start studying the basics of Magnetic Induction and Electrostatic Induction and how they relate to one another in reality versus your textbook theory.

Now go back to the image on magnetic induction I posted until you actually understand it, my 10 year old son does so I am sure you can.

AC

[MarkE]

@Mark EAh I see the problem you are thinking of Electromagnetic Induction and I am speaking of Magnetic Induction.
Magnetic Induction: 1.The process by which a substance, such as iron or steel becomes magnetized by a magnetic field. The Induced Magnetism is produced by the force of the field radiating from the poles of the magnet.That was what I was using when I made the measurements, an analog hall effect sensor as well as a hall effect sensor array I built as I stated in my prior posts. Your not listening and inferring things which are incorrect. I did not say induction I specifically said "Magnetic Induction" which is a very simple and well know fundamental principal known to most everyone who understands basic physics. A permanent magnet having a magnetic field will induce a magnetic field of opposite polarity in a piece of iron within it's field of influence. The induced magnetic field in the iron is considered as a separate magnetic field in itself and can be measured as such even though it is a function of an external field.
To make my point, I try to avoid superficial observations which tend to confuse even most experts and concentrate on Primary Physics. This is the primary field phenomena such as the Electric, Magnetic and Gravic fields in their most fundamental forms. It avoids all the confusion I am seeing here and concentrates on the most fundamental interactions between the Primary Fields. You need to start studying the basics of Magnetic Induction and Electrostatic Induction and how they relate to one another in reality versus your textbook theory.

Now go back to the image on magnetic induction I posted until you actually understand it, my 10 year old son does so I am sure you can.

AC

Do you understand that you just killed your own argument against iron filings?  By inducing a pole that is opposite polarity, the magnetized soft iron reduces the reluctance gap between the poles.  Ergo the field set-up by the newly magnetized soft iron only intensifies the field that was already in the region of the dipole they surround.  Ergo their alignment does in fact correspond to the field direction.  Ergo since they do not turn towards the dipole at the dipole center, the proposition that the field turns there is false.