Demonstration of magnetic viscosity

[perazaroberto2]

good new thingh

[MrBoris12345]

This is NOT viscocity. Electronic ferrites simply do not have the appropriate single domain grain size (<30nm). Rather, this is simply an AC signal from hall due to the measured magnetic field being increased by the presence of the magnetically permeability of the ferrite as it passes by; and the closer it is to the magnet, the higher the magnet-ferrite-hall coupling, so the higher the signal.

[Eltimple]

interesting , but the same test can be done static, firng a coil at one end of a ferrite rod, and timing the wave along the lenght, you will find much the same result. I belive static testing is better but not as much fun to video..

[broli123]

@Eltimple

I was looking for that exact same experiment. Have you actually performed this?

[Eltimple]

@broli123 , yes about a year ago,

[gilbondfac]

steorn motor

[lumen0]

You may also want to try rotating the disk with the ferrite in the opposite direction to rule out any affect of the ferrite becoming magnetic just from the close proximity to the magnet and simply directing the field into the hall sensor.

[kerelwtf]

man, all these cool experiments you do!

Is this your job or your hoby?

and if it is your job, what job is it?

grtz

[Lokivoid]

Considering his cheap makeshift oscilloscope and lack of understanding of physic's or electrical engineering. I would say he is a amature hobbyist that doesn't have the clue about what hes doing or why it wont work.

[Eltimple]

You show a lack of understanding of the content of the video, we are not saying anything will or will not work, we are demonstrating Magnetic viscosity.

[sacha4you]

Eltimple, congratulations! You have just re-found again the basics of the laws about time variant magnetic remanence!

This is the shocking-secret explanation, why the core-power density [W/m³] is much lower for a 50/60Hz- mains-transformer, than for a 50...100kHz transformer in the SMPS (Switched Mode Power Supply) in your computer. When you work hard enough, you will re-invent one day Maxwell's laws. Good luck!

;-))

[Eltimple]

LOL, seeing these effects like this hopefully makes it easy to understand. i wish my physics prof had done it this way to demonstrate bh et al.

[Thorsupremecommander]

either way, clip is interesting, because phenomenon may be explained at least in two ways.

(I) magnetic rod  is magnetized by perm magnet and produces 'reactive" magnetic field - hall sensor doesnt detect revolving perm-magnet

(ii) it is aetheric magnetic remanence (aspden states about that concept)

[Thorsupremecommander]

I admit I don't grasp the point, why you call it viscosity of magnetic field? do you mean by it - thickness, volume of magnetic field?

[Eltimple]

Viscosity because it is not "On" or "Off" in an instant. Th ferro magnetic material "Charges" up with magnetism then looses it over time, Look at a BH curve to see what i mean

[Eltimple]

Yes, Even down to the earths magnetic field in a car compass

[AClarke2007]

I don`t think Hall Sensors detect stationery Permanent magnetic fields do they?

[Thorsupremecommander]

they do sense stationary magnetic field :) both types of them (analog and digital)

[inglishspeeker]

the best part is his accent.

especially the way he says "dodgy"

peace

[commengr]

Interesting. Especially in that there appears to be a reversal in the ferromagnet polarity as the signal falls below the baseline. Or is there some other explanation for the sinusoidal waveform?

[Eltimple]

as the ferrite passes the hall in an arc it is sees the inner most face of the ferrite as it goes away . This produces a dip to the other polarity on the trace. This is not visible on entry as the charging magnet is affecting the near field

[AdminOnDuty]

I don't think we are seeing magnetic viscosity here. In order to show magnetic viscosity we need a timing reference so we can see the differential between the time the ferrite enters the field to the time it becomes fully magnetized by it.

This should be renamed "Relative Measurement of Magnetic Induction"

Great demonstration otherwise! Thumbs Up !

[nickeca]

Hey AOD. The time component is clearly the amount of time it takes for the magnet to get to the hall sensor.

Since this time is being varied when then sensor is positioned at various distances, and we know the rpm, we can calculate lag.

I respectfully disagree with you proposal to rename. It is definitely not a "relative measurement of magnetic induction".

Sorry. No disrespect intended. :)

[AdminOnDuty]

No worries ;-), Here is the issue: We do not have any mark for the 'full' magnetization of the ferrite. Therefore, instead of measuring 'lag' all this rig is doing is measuring proximity of an induced field which is at maximum when the ferrite is close to the magnet. Viscosity is the time differential between immersion in a max field (H) and full weiss domain alignment resulting in full magnetization (B). This apparatus does not test for this. It doesn't even show demag time. No disprespect ;-)

[Eltimple]

You are quite right in mentioning the field from the stationary magnet , which will affect the halls readings when the hall is very close. But in practice it did not prove to be a problem on this crude setup, the halls "window" is pointing towards the rotor, and the hall did not pick up anything from the stationary magnet even when touching.But if serious in measuring this effect try and do it stationary.

[knowledgemonger]

Great experiment but I think there may be a bit of an issue with the field from the magnet.

You need to have the magnet's field be zero at the point where you are measuring the field in the ferrite. If it isn't, so the the field you are seeing will be an induced field.

Another way to attack it would be to vary the speed of the disk and keep its angle constant. This would require that the sound card's frequency response not be messing up the shape.