Shielded Magnet Characteristics Part 1

Using Roney's configuration we made two shielded magnets and here attempt to demonstrate some of the characteristics of this uniquie geometry.

Category:

Science & Technology

Tags:

• Magnetic
• Shunt
• Shielding
• One-Way
• Unipolar
• Coaxial
• Field

[fuelban]

These shielded magnets are called "POT MAGNETS", you can purchase them from good suppliers, they put most of the force out the front end... they come Trade supplied with a bolt /"Threaded Stud"- protruding at the back end for fixing, they have been around for some many decades now, whilst they are slightly more expensive, you might find less hassle purchasing than making guys, hope this helps.

Thom in Scotland.

[AdminOnDuty]

@fuelban

Hello Thom, again. You are the same fellow that tipped us off to these Pot magnets a year ago . . . remember? (Just scroll through the posts) ;-)

After your post, I did purchase the 'Pot' variety and even have one here still in the package:

General Tools MFG - Shallow Pot Magnet 20 Lb Pull No. 376B UPC 42114

It is 2" in diameter ~1/4" thick and has a 3/16" Hole.

But it has quite a bit of back attraction unlike those I constructed with the triple shielding.

Cheers!

[fuelban]

@AdminOnDuty > LOL, Sorry about that, Interesting to note your construction has less back attraction.

thanks

thom.

[AdminOnDuty]

@fuelban

No worries =)

We welcome the comments!

I think the reason has to do with the gap between the layers having a lower permeability and the flux path having to change orientation as it transits from and into the shield material. Or maybe my shielding simply had a higher average permeability overall. Or, perhaps the square design had some impact on the back flux. It would be interesting to plot the flux density on various types and see how they compare.

Cheers!

[fuelban]

@AdminOnDuty > My own experience "though Being Slight", Would side on your statement of the gap between each layer, if I were to put forward a view, it would be to make that first layer close to the magnet of high permeable metal, and increase the gap between on the 2nd, and so on to the 3rd layer respectivly. I found magnetic force, likened to electrical force, LAZY, taking the easiest, and quickest ,route oot. willing to take guidance if offered...

Thom in Scotland.

[AdminOnDuty]

@fuelban

You are correct that magnetic flux prefers the path of higher permeability.

Search wikipedia for 'Magnetic Reluctance' for the formulas related to this concept.

There you will find that Reluctance = material length in meters / (divided by) permeability of free space * (times) permeability of the material * (times) Cross sectional area of the material in meters square.

Fancy R = ℓ / µoµr A

Φ (magnetic flux) = Fancy F (magneto motive force) / (divided by) Fancy R (Reluctance)

Cheers!

[AdminOnDuty]

@Risenangelicaegis ,

LOL - IIRC, I shot that with a cellphone camera =D

But, in one of my videos, I did use a rubberband to secure the cellphone to a tripod, so it goes to show that it can be done.

My sincere apologies to anyone who was so preoccupied with the cinematography and physiological inverse kinetosis it may have brought on that they missed out on the magnetic effects and general presentation. The best method to prevent this is to repeat the experiment(s) first hand - ;-)

[Risenangelicaegis]

PUT THE CAMERA DOWN - AND STEP AWAY FROM THE DESK…………OK

DON'T worry I was only MOTION Sick 4……No wait ………5 times during that video maybe it would be safer if you put the camera on a book near your arm on the desk or something ? Or maybe a mini tripod made from some old fence wire or something ?

[AdminOnDuty]

@daenumen ,

Not only have you failed to observe the details, but now you wish intimate that I have claimed to shield magnetism - no such claims exist. It is one thing to shield a magnet and quite another to shield magnetism (the latter being technically impossible). Shielding a magnet from light and heat (among other EM sources) is quite easy as I have demonstrated. Shielding an object from a magnetic field is a misnomer because the best you can hope for is flux redirection. Your Blocked.

[daenumen]

@AdminOnDuty i did watch the entire video actually, these effects are still not 'flux pinning', this is a phenomenon believed to occur with superconductors.

after 7:00 you did not explain the phenomenon, you just show it again. the phenomenon seen at 2:38 is the one you describe, however it is not because of magnetic shielding.

the cause is obvious, once you realise you are not 'shielding' any magnetism.

good luck!