Light, thin but strong magnet?

[ASoteldo]

Hi everyone!

My knowledge of physics is very very basic, so I just found this great forum and I think it would be great to have a feedback from people who know.

I am in development of a project that involves a laptop sleeve and some magnets. I've already done my research and found that they doesn't really affect functioning of laptops unless they are really, really strong.

All over the internet, the answer is the same: neodymium magnets are the best choice. They are strong, light and come in many thicknesses, which seems to fit my needs. But here comes my questions:

1) How much does the thickness of the magnet affects the strenght of it? A lot? Not even too much to care? The idea is to attach things to the sleeve and, if wanted, carry it in a bagpack without concern of things falling from the sleeve.

2) Is there any way to isolate one of the "faces" (polarities) of a rounded neodymium magnet so it won't even "touch" the laptop? I mean a light and very very thin solution, like a coating or something if posible.

3) What happen if I put a lot of them across the sleeve in, let's say, squared enclosures? Are they going to start atracting one another? Is there a minimun distance I should keep between them?.

4) Are neodymium magnets "water resistant"? They will rust if the sleeve is washed by hand?

5) As I said, my knowledge is pretty basic, but I am really excited about learning. Any suggestion is widely welcome.

I am not sure if this is the correct section to post this thread, if is not, I would be pleased to be notified where I can post it.

Thanks a lot in advance. I am really pleased to find spaces like this one around the internet.

ASoteldo.

 

[davenn]

hi there
welcome to PF

1) How much does the thickness of the magnet affects the strenght of it? A lot? Not even too much to care?

I would expect that the more material, the stronger the magnet

2) Is there any way to isolate one of the "faces" (polarities) of a rounded neodymium magnet so it won't even "touch" the laptop? I mean a light and very very thin solution, like a coating or something if posible.

Isolation of a magnetic field is very difficult ... maybe a mu-metal shield

3) What happen if I put a lot of them across the sleeve in, let's say, squared enclosures? Are they going to start atracting one another?

yes

4) there a minimun distance I should keep between them?.

you would have to experiment with the particular ones you decide to buy
the distance will be proportional to strength

Are neodymium magnets "water resistant"? They will rust if the sleeve is washed by hand?

they are plated ... chrome, I think ... the chrome won't rust etc, but if it is chipped then the material below will be exposed to the moisture and goes a sort of rusty brown, going by the one I have here on my bench

I am not sure if this is the correct section to post this thread, if is not, I would be pleased to be notified where I can post it.

Thanks a lot in advance. I am really pleased to find spaces like this one around the internet.

yup a good place

hope that helps Dave

 

[Fervent Freyja]

1. More is not always better. The thickness, not length, will determine the strength of the magnet.
2. A piece of cloth covering that side will do.
3. I assume that you are using magnets to keep the sleeve closed, you want them strong enough to prevent the laptop from sliding out, but you probably won't need to place so many that a few end up in the unintended positions (a long strip on each side would probably work and prevent that from happening).
4. They should already be surface-treated when you buy them, so don't grind them down or anything. It should be fine going through the wash, I have some garments/purses, even kids shoes, in my household that hold neodymium magnets.
5.This is good brand that my Husband has ordered for heavy duty projects. Block magnets attract at the sides too, which will allow you to place them side-by-side in a strip. These 2.5mm magnets have a pull force of 2.4 pounds, while the 3.2mm have 6 pounds. You may want to decide first depending upon the weight of the laptop, it should be able to stay clasped shut hanging upside down with the weight of the laptop against it (get aggressive with the sleeve for an extra measure to ensure it will not come unclasped). You may need to go stronger than those above. But the thicker ones will be bulkier, and you might want to keep in mind that stronger magnets may cause damage if they attract each other too quickly (not good if someone decided to use a tablet instead). You can order the same brand off other online retailers if you cannot find any in your local area.

 

[davenn]

2. A piece of cloth covering that side will do.

only if it is physical separation that is wanted, else the magnetic field will penetrate the cloth as tho it isn't there

...tho his definition of touch was very vague
@ASoteldo what is your definition of touch in this case, magnetic shielding or just physical separation ??

Strong magnets against a laptop is not a wise idea... the magnetic fields could do substantial damage
Dave

 

[Fervent Freyja]

only if it is physical separation that is wanted, else the magnetic field will penetrate the cloth as tho it isn't there

...tho his definition of touch was very vague
@ASoteldo what is your definition of touch in this case, magnetic shielding or just physical separation ??

Strong magnets against a laptop is not a wise idea... the magnetic fields could do substantial damage
Dave

Yes, if the magnet is strong enough, it will still attract through the cloth. Trust me, I have done lots of craft projects, it works. Manufacturers often use cloth over the magnet because it can be a choking hazard in products for children (if the magnet came loose). I have handbags with only one weak magnet that can support the contents of the bag (upside down) and have not had any issues with that magnet damaging my electronics inside...