Magnet Myths and Misconceptions

[MarkE]

A misunderstanding there TK,as you said-Quote: .But also of course you will be able to do work by spinning a coil of wire in the same position as your "forceless" probe or non-acting reed switch: See "electric motor" in  WIKI

The coil of wire produces magnetic fields !dose it not!?,there for you have introduced two more magnetic fields.
.

Yes,it shows flux in the center,but both the value of that flux and it's strength is 0.

Again this is wrong.  There is really and truly a good deal of flux near the magnet mid point.  The orientation of that flux is all parallel to the dipole.  If you watch a fast moving stream that runs exactly north to south, what is the flow rate east to west?  Does the fact that there is no east-west flow make the flow rate in the stream north to south any less than somewhere up stream or down stream there is a bend that turns east or west?

[tinman]

.
MileHigh

Anyway, I can see that Tinman is close to getting a better understanding.  I note it looks like he has a notion of 'north flux' and 'south flux' originating at each pole and where they meet half way they 'cancel each other out' and then there is no 'useful field' there.

TinMan has always had the correct understanding. I have posted !how many times?! the highlighted in the above quote. I have said time and time again that the useful magnetic field is in the shape of a figure 8/peanut.

I think a few simple drawings would aid in people's descriptions from time to time.

Im not sure how many more drawings you would like me to post,but i will post one useing water,pipes and a pump that fully explains what TK show's with his hall sensor,and why he shows a continual flux along the length of the magnet. The flux is there,but a defined magnetic field(north or south) is not.

I have been talking about the effective magnetic field all along,as i have mentioned in many post.

[itsu]

Not exactly. In the scan with the sensor at right angles to the long axis of the magnet stack, the "dip" and the "peak" are indicating exactly or pretty much the same flux density, just different directions wrt the sensor plane. Recall that the center, or zero baseline, of the scope trace is indicating _zero flux_ through the plane of the sensor, and positive deflection indicates flux in one direction wrt the sensor plane, and negative deflection indicates flux in the opposite direction. The difference between "peak" and "dip" only indicates the direction of the flux through the plane of the sensor. This difference is because the sensor is flipped 180 degrees from one scan to the other, so the flux passes through it in the opposite direction relative to the sensor orientation. The "peak" and the "dip" in Itsu's video are showing the point where the field lines are the most parallel to the long axis of the magnet stack and have the least density, just as shown in the conventional picture of the field lines. If the "peanut waist" picture were true the data would be very different than what Itsu has demonstrated. All of the above paragraph refers to the scans where the sensor is held at right angles to the long axis of the magnet stack.

When the sensor is held so that the plane is parallel to the long axis of the magnet, the sensor output goes to zero or rather the zero baseline of the scope trace, indicating _no flux through the sensor_ at the center of the stack. This means that the field lines are parallel to the plane of the sensor at that point, fully confirming the conventional view of the field lines. If the "peanut waist" view were correct, there would be a maximum reading (well above the baseline) just to one side of this null point and a minimum reading (well below the baseline) just on the other side. But this is not what happens: the maximum reading occurs at one pole, grading smoothly to zero at the center, and grading smoothly to the minimum reading at the other pole. Very different from what is predicted by the "peanut waist" or "Bloch wall" picture.  The above paragraph refers to the scans where the sensor is held with the plane parallel to the long axis of the magnet stack.

I think Itsu's demonstration might be more stable if he used the wide part of the magnet stack instead of the narrow part. You can see how difficult it is to hold manually the proper orientation of the Hall sensor, and deviating slightly from the centerline of the narrow face of the stack causes fluctuations in the reading from the sensor. This effect would probably be less if he scanned the wider face of the stack.

Itsu's demonstration appears to me to be reporting the identical picture of the field line direction and density that my own demonstrations provide, and is refuting the "peanut waist" picture and confirming the conventional picture of the direction and density of the field lines around the stack of magnets.


Part 2, the parallel scan of my magnet stack, will be viewable in a few minutes:
http://youtu.be/OTe4rNwrZKY

http://www.youtube.com/watch?v=OTe4rNwrZKY

Ok,  wide part of the magnet stack scanned, sensor fixed from above, sliding the magnet stack underneath it (1cm)

https://www.youtube.com/watch?v=n-5WxjH8IqM&feature=youtu.be

Regards Itsu

[tinman]

Koala,
        You've got an inventive sort of mind. Is there any way you could arrange
your magnets to give a "figure of eight" to satisfy Tinman's aspirations?
             John.

Are you at it again John?-having a shot at me?. You dont have to rearange anything to see the figure 8 field.

[tinman]

I agree, it looks like that, but thats probably because my hasty video job on the upper flux, in reality its different, see this new short video:


https://www.youtube.com/watch?v=zShIcIsvBS4&feature=youtu.be


Regards Itsu

Thank you Itsu,TK and AC for doing these test. Different results from TK to that of Itsu and AC,so where dose that leave us?