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Would a strong magnet have any effect whatsoever on a thumb drive (I'm assuming not) or on an SD card? It seems unlikely, but I'm hoping someone can give me a definitive answer, since I'd rather not find out the hard way that it actually can. Assume the magnets are powerful industrial magnets, if that makes a significant difference to the answer.

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Depends if it is a static field or an alternating field (in case of electromagnets) – jippie Jul 31 '12 at 20:52
@Danny: yeah I didn't think to look on SuperUser, since the primary dimensions of the question seemed to me to be about physics and electronics. I chose electronics since the physics site seems to focus on theoretical issues. But perhaps those other questions were asked before this site existed, so the other questioners had no choice but to use that site. – iconoclast Aug 1 '12 at 19:29
like a the field of energy created by a small electric motor if the card was against it for day... would that possibly ruin it or destroy data....? i stashed an sd card inside a small wind up torch for purposes i cant disclose but i believe upon using the wind up motor to generate light while the card was hard presses against the side of it may have had an effect but I am still trying to re-retrieve the data... Help...? – user17863 Jan 13 at 20:20

5 Answers

up vote 11 down vote accepted

I've tested many card with my 1.5Kg rare earth magnet, so I can bet that magnets have no effects on flash cards or USB pen drives :-)

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+1 because you own the 1.5kg rare earth magnet :) – woliveirajr Jul 31 '12 at 20:04
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What is your field strength on that magnet? – Kortuk♦ Aug 1 '12 at 4:49
@Kortuk I can't measure those parameters (and, beside Tesla, I don't even know those measure units :-) ), but on the specification sheet there are some informations. Resudial Magnetism: 1.22T, Coercitive field strenght: bHc 860 kA/m, jHc > 1592 kA/m, Energy Product: 287 kJ/m3 – Axeman Aug 1 '12 at 6:43
up vote 9 down vote

For venerable floppies, this statement holds true. We placed a 99-cent magnet on a 3.5-inch floppy for a few seconds. The magnet stuck to the disk and ruined its data.

Fortunately, most modern storage devices, such as SD and CompactFlash memory cards, are immune to magnetic fields. "There's nothing magnetic in flash memory, so [a magnet] won't do anything," says Bill Frank, executive director of the CompactFlash Association. "A magnet powerful enough to disturb the electrons in flash would be powerful enough to suck the iron out of your blood cells," says Frank.

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The only thing that would make this answer better is to include reference information, a link or issue information such as publication date and page, to the article quoted. – Joshua Drake Jul 31 '12 at 20:12
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The iron in hemoglobin is non-ferromagnetic, so a magnet will not "rip the iron out of your blood" in any case, actually. – Connor Wolf Jul 31 '12 at 23:31
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This is just a copy and paste job from the article, treating the article's text as though it is your own. You link to the article as if you are directly linking to something Bill Frank wrote, but that's not the case. This seems like borderline plagiarism, only saved from being complete plagiarism by the fact that if someone follows the link they'll see that the entirety of your text is from the linked page. – iconoclast Aug 1 '12 at 19:24
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Besides being just a copy-paste job, it comes from the article I already linked to before you posted your answer. – iconoclast Aug 1 '12 at 19:30
Surely if you were to move a magnet over the card sufficiently fast then it would induce some currently to flow in the internal wires and conductors despite "There's nothing magnetic in flash memory"? I – John Burton Aug 2 '12 at 8:10
up vote 5 down vote

Assuming you are talking about ordinary magnets, no.

If you are talking about the field strengths found in an MRI machine or a fusion research device, things start to get weird - there's the hall effect, potential for induced current due to movement or field changes, even potential for mechanical distortion and having parts ripped out of the assembly.

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up vote 2 down vote

Magnets will not, according to the gurus at PCWorld, affect your SD cards, since they are just flash media (like thumb drives).

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up vote -1 down vote

Flash memory of either SD cards or other usb sticks, are advanced version of EEPROM, Which is only be eraseable electrically. means you need electrical methode to erase or destroy flash memory

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