How Does it Work?

[Ian Anderson]

Hi

a friend of mine asked if I had any idea about this and drew a total blank

Anyway herewith how he put it

I’ve been struggling with a silly problem that has been troubling me for a few weeks now regarding magnetism.
I recently bought a cheap, Chinese Magnetizer/De-magnetizer from EBay, to de-magnetize the tweezers and screwdrivers that I use for clock repairing.

I remember from physics lessons at school that a steel item can be magnetised by stroking it with a magnet and to de-magnetise it it can be repeatedly struck or heated to above its Curie temperature.
Another way to magnetise something is to place it in a coil and pass a direct current whilst an alternating current will remove the induced magnetism.
For demagnetising, I’ve successfully used a Weller mains electric soldering gun which heats the tip by making it the secondary of a transformer.

The item to be de-magnetised is passed through the space between the two arms with it switched on, slowly removing it and then switching off.
My Chinese device obviously uses a permanent magnet for the MAGNETIZE aperture but what’s in the DEMAGNETIZE aperture remains a mystery to me.
At college we had lectures on magnetic domains and atomic theory and things like unpaired electrons but this was all a bit too complicated for me to take in and I had to content myself with a superficial, empirical understanding of electricity and magnetism.
This has been bugging me and I might be forced into sawing it up, although I have a feeling that this might well not help me very much.

I’ve asked several people about this but nobody has yet provided me with anything like a satisfactory explanation.They use a lot of impressive words and references to links on the internet that turn out to be unhelpful to the point of naivety!
I will freely admit to my ignorance of quantum mechanics and atomic theory but I can smell bull***t at 100 paces and so I would love to find out what the Chinese have done to make something that is inexpensive but does what it claims to do.

Item's Picture attached


So can anyone assist Roger?

Thanks

 

[Paul W]

How does a tool demagnetizer work? - Quora

 

[David Morton]

Positively or negatively polarised and the action of drawing the tip or plade through the tool leaves is magnetised ore demagnetized.

 

[Ian Anderson]

Thanks guys but I believe Roger is looking for a bit more information - he is a published metallurgist and will have thought this through already. (For reference he worked with Mirage and took ZF to Court for failing shafts in their transaxles. (So he knows a fair amount about metals)

David your explanation sounds great but how does it decide which polarity it is already so it then either adds t or destroys that polarity depending on which "hole" the item is put into

Cheers

Ian

 

[Mike Pass]

I would guess that there are pair of pole in the demagnetiser section so that as you pass the item through it is first magnetised in one direction and then then promptly the opposite way. Alternating current demagnetises the same way by rapidly reversing the magnetising field. This shakes up and randomises the magnetic domains in the material. Moving the material through two directions of magnetic field has the same effect by reversing the magnetising influence as it goes through the opposing magnetising influence in quick succession. The more rapidly this is done the better. There will always be a very faint residual magnetism left by the last field it passed through but this is very weak and equivalent to magnetising with a single stroke of the magnetising magnet.
Heating also randomises the magnetic domains and the net effect is no apparent magnetism. To get the best effect the material should be cooled where there is no net magnetic field otherwise the earth's magnetic filed will magnetise the material as it cools. Banging steel in the earth's magnetic field will cause it to become magnetised which is why steel ships which remain in one position during the build are magnetic and will set off mines which detect this magnetic field. As this will also affect the ships compass small magnets are set round the compass inside the binnacle to exactly counteract the ship's magnetic field. Bashing the steel in random positions would jumble the domains again and effectively demagnetise the item.
The magnetic domains are crystalline areas where the atomic dipoles are aligned. They remain magnetised even in apparent unmagnetised material. When they are random they cancel each other out. Magnetising sets the domains magnetic direction into alignment. If you place a microphone onto a bar of material and then magnetise it and amplify the sound you can hear a series of clicks as the alignment of the domains changes.
Cheers
Mike

 

[Keith]

So essentially, the tool is a 'Randomiser.'

 

[Robert May Eng.]

Is magnetism not a bit like electrickery in that we now how to produce and utilise it but cannot put into words what it is :blank: :huh:

Bob