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When I first started using computers, law of the land in computer class was never bring magnets near anything computer related, lest you lose all your data or screw up your monitor.

Now I am pretty sure magnets will still royally mess up a standard hard drive, and I know for a fact they screw up a CRT monitor.

Though I am also pretty sure they do not screw up a LCD monitor?

Now I have my phone which uses magnets to determine if it's docked, and it made me wonder.

Is it the power of the magnet preventing data loss or the sheer fact that whatever memory type in the phone is immune to it?

What about ear buds, as I know those have tiny magnets in them. Are those capable of damaging any electronic device currently in use?

I'm wondering if I'm being paranoid, but I really am not sure what magnets will damage and what they won't!

Is there a list, or rule of thumb for determining what will be hurt by magnets and what won't be?

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I recall sitting at a computer on a major particle physics experiment when the big (10x5x3 meters, >100 tons) dipole magnet was being tested about 40 meters away. As they ramped it up the display would twist to one side by about 10 degrees. Hit "degauss" on the monitor front panel, ::blur:: then return and all would be well. Later, they'd ramp down, and the monitor would twist the other way...good times. Leave you wallet in your pocket and walk into the hall while they were doing that and you'd loose the data on the magnetic stripes on all your cards...bad times. –  dmckee Feb 25 '10 at 18:22
    
Thanks everyone for your answers, really helped me gain a better understanding. –  Brett Allen Feb 26 '10 at 15:42
    
Nobody has talked about these yet: Cars (and their contents ie gps, radio, etc), tools (chainsaws, drills), kitchen appliances, ceiling fans, etc. Any caution to take with those? Also, could a magnet induce enough magnetism in another metallic object to make that object dangerous? And lastly but mostly, are there any methods of avoid the negative effects of magnets ? (such as enclosing them in a faraday cage or something like that). Sorry for highjacking your question Aequitarum, but mine was closed as a duplicate.. –  Shawn Nov 30 '10 at 20:00
    
@Shawn The normal magnets you will find around an average house will not do much to modern electronics for reasonable exposure levels (there is an exception for particularly senstive things like floppy disks, and CRTs). So, an average consumer does not need to worry about it. For your not so average consumer, Wikipedia has a good write up at en.wikipedia.org/wiki/Magnetic_shielding –  TimothyAWiseman Nov 16 '11 at 19:36
    
Stick any computer component inside an MRI machine and you can kiss it bye-bye. –  Daniel R Hicks Oct 5 '12 at 18:19

13 Answers 13

up vote 9 down vote accepted

Hard drives, RAM chips, power supply, anything electrical can be vulnerable to magnetic fields.

In common practice it's not all that harmful unless you're doing it on purpose. Case in point is the magnet MacBooks come with built in to use with the power supply.

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weak magnets + good shielding = no problem. strong magnets + unshielded hdd = bye-bye data. –  quack quixote Feb 25 '10 at 18:34
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@quack: Every hard drive I've ever taken apart had 4 strong (rare-earth) magnets inside that help move the arm with the read heads back and forth. What you need to harm a HDD is a magnetic field (not a permanent magnet) so strong that it takes 5 minutes of 120 volt current to charge the capacitor that discharges through a coil in less than a millisecond to create the magnetic field to wipe the drive. These machines cost a ton of money. A hard drive inside a metal case is pretty safe - until you put it in one of these. –  hotei Aug 23 '10 at 11:49
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This is completely false. Hard disks care because they rely on magnetic fields to store your data. Most electronics, including ram and power supplies don't give a flying fig. –  psusi Jul 19 '12 at 18:57
    
I heard that the best way to decorate your computer is to put hundreds of super strength magnets on the case!!!!! No. As long as you're not dumb or trying to destroy your computer, I doubt that anything bad would even be possible. –  Annonomus Penguin Aug 4 '13 at 16:01

A list or rule? Sure, anything that uses electro-magnetism to function could, and would be affected by magnets. The question is what the detrimental effects, if any, would be and how strong and close do the magnets need to be. Generally the two most questioned items are the monitor and disk drives.


LCD/LED monitors are not generally susceptible to magnetic interference like CRTs are because they function completely differently (remember, CRTs use magnets to deflect the electron beam, so an external magnet would obviously mess with that).

Hard-drives are also not affected by magnets because of the way they function. You can research the details on how hard-drives work for a more thorough understanding, but the easy answer is that there is a very powerful magnet inside each hard-drive that controls the read-write head’s movement. That’s why some people like to rip open dead drives to get at the sweet, gooey super-strong magnet inside. If that magnet that is inside the drive, and right beside the platters doesn’t wipe them, then any magnet that you are likely to have around isn’t going to.

As for flash drives, they are a different technology altogether so they are not going to get erased.

There is one component however that is indeed affected by magnets that most people miss: cables. While many cables are shielded, some are not and thus susceptible to a magnetic field. For example, a cable connecting the sound card to the speaker may be shielded, but the little cable connecting the CD/DVD drive to the sound card usually isn’t and ingress of a magnetic field could cause interference. Or, while rounded IDE cables (especially for IDE133) are usually shielded, ribbons usually aren’t and even at speeds of 66/100 could be affected enough to cause some corruption or at least reduce performance due to re-tried reads/writes.


I would say that modern systems are not really vulnerable anymore because as time progresses, science and knowledge advances, but unfortunately that’s not sufficient. While that may be true, in the old days things were done right a lot more than today with all the cut corners and cost-reducing measures (eg NVIDIA’s “Bumpgate”).

Anyway, the point is that when it comes to modern computers (I’m counting floppy disks as not-modern), you don’t really need to worry about magnets. You can breath a sigh of relief. :)

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I'm a little concerned about your assertion that HDDs are immune to strong magnetic fields. They do indeed contain very strong rare-earth magnets, but they are aligned in a particular way, and shielded so that most of the magnetic field is contained. In other words; I'll let you try running a magnet over the surface of the disks first! :) –  aidan Apr 19 '13 at 1:38
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@aidan, it has been discussed in numerous places countless times and the consensus is that anything short of a very powerful magnet (I recently read about a company that sells super electro- and permanent-magnets that can wipe drives, but I don’t remember where) will not likely do much to a hard-drive. I clearly said that any magnet that you are likely to have around (i.e., fridge, speaker, shower-curtain, etc. magnets) won’t have an effect (at least not by accident; opening the drive and swiping the magnet directly on the platters is not what this question is asking). –  Synetech Apr 19 '13 at 20:27

I've passed a standard size 512GB HDD through a magnet strong enough that I couldn't pull a chunk of metal off it, and it functioned absolutely fine afterwards (And does to this day, as far as I know) - I think it's safe to say hard drives aren't that susceptible anymore.

(CW because this is, obviously, not proof of any kind, just my experience. I do not endorse the using of magnets on 512GB HDDs, use them to store media or something if you really don't want it :P)

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+1 karma for making it CW yourself ;-) –  Ivo Flipse Feb 25 '10 at 20:12
    
@Ivo: -1 for not really +1ing the answer. –  Hello71 Aug 28 '10 at 15:01
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It is about the strength, duration of exposure, and relative motion of the magnet with the harddrive. Weak magnets will generally not do anything, relative strong magnets for a short time won't do much. A strong magnet, for a longer period of time, especially if it is in motion relative to the electronics will corrupt the data (and a really strong magnet in motion for a long period of time can fry just about any unshielded electronics.) (Edit for clairty: By strong I mean far stronger than most people have lying around. Even old harddrives are more reiliant than most people think.) –  TimothyAWiseman Nov 16 '11 at 19:16

You're being paranoid. It would take a pretty significant magnet to permanently affect most parts of a computer these days. As long as you're not working around industrial magnets, or sticking things to the side of your case with powerful rare earth magnets, you should be fine.

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If it's electric it can be affected my magnets.

That said most electronics today is pretty well shielded so if you don't stick your magnet to stuff or let it rub against it for a prolonged time you should be pretty safe.

And your phone does not use magnetism to store data on a disk, it uses an internal flash card.

The only thing that I can think of that could (in a reasonably scenario) be hurt by a magnet is floppies and cards with magnetic strips.

This is of course with normal household magnets.

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At my work we found an old floppy disk with a pretty powerful magnet stuck to it that'd been that way for years. I could still read off the floppy just fine.

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Rarely a problem anymore. Higher bit-density requires higher coercivity, which results in greater resistance to "accidental" magnetism. Old single density floppies could be wiped out if you ran them over with a vacuum cleaner. Newer hard drives are quite resistant to erasure from anything you're likely to have laying near the computer at home...

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From my experience, very little damage can be expected unless you get a strong magnet near an unshielded coil of some sort that's on a circuit board. This can significantly disrupt the magnetic field that surrounds this component, at least enough to change the voltages that it is involved with cleaning or adjusting. It most likely won't 'fry' a circuit, but it could cause it to over-heat due to voltage changes which could lead to component damage and board failure.

Case in point, I added a strong magnet to the bottom of a USB hub so it would stay in one place on top of my computer case. After a while I noticed that it was getting significantly hotter than the exact same hub that didn't have a magnet attached to its base. After removing the magnet, it went back to normal fortunately.

Contrary case: I have a terrific battery tester, 'Batt-O-Meter', that "loads" the battery being tested, then processes some additional information to give you not only the actual voltage (in digital form), but it also indicates the effective percentage of power left in the battery, a more significant factor when you're considering how much longer a battery will last, or how efficient your rechargeable batteries are at being charged.

I attached the magnet to the main 'positive' post on the device so any battery I'm testing will stay connected to that post with little effort by me while I'm using both hands; one to press a button and hold the battery, while holding the wired probe against the 'negative' post. I've been checking whether there has been any deviation of the resulting readings due to the magnet and so far there hasn't been, and of course, no over-heating as in the other case.

There's no way to tell how much interference will occur until you do a trial with and without the battery in the vicinity of the device. Momentary exposure will surely not hurt most circuits.

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For the most part, none. The typical magnetic fields we encounter every day are not a significant issue for most electronic devices. For example, speakers are electromagnetic devices, and they are often mounted on laptops very close to other computer parts without any problems.

Most electronics can be damaged, however, by strong and rapidly changing magnetic fields. As I've written in this answer, changing magnetic fields cause electromagnetic induction, and if sufficiently strong, could cause the circuits to carry damaging amounts of electrical power. However, this isn't going to happen under normal operation, and speakers (which do generate changing, although weak, magnetic fields on top of a permanent magnet) and other household and office magnetic objects is not a significant concern.

Hard drives are quite resistant to outside magnetic fields despite internally relying on minute magnetic fields to store data. The case of the hard drive provides resistance against electromagnetic induction and transient magnetic fields because it is conductive and therefore acts as a Faraday cage.

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hard drives and crt would probably be mostly severely affected.

i suspect the most would need some kind of modulating magnetic field to create sufficient inductive properties

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There's a similar question on Yahoo! Answers:

Do Magnets damage Electronics?

Do Magnets damage Electronics?

I have a few electronic devices that have cases that have those magnet that help close and lock the case but I was wondering since the device is right next to my mp3 player or cellphone does it do any harm to them? Because sometimes you see in movies the magnet damages the memory or something.

Best Answer

Magnets can an do harm ANY magnetic media....tapes (audio & video), minidiscs.

They WILL also harm hard drives, static memory (cell phones, Ipods).

I would put your static devices somewhere away from any magnetic fields such as speakes as well.

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Seriously, how does this answer not get voted up. +1 For pointing the authoritative source on the matter. I bow to you sir, well done. –  John Sonmez Aug 15 '11 at 4:40
    
@John - Link only answers aren't useful as links often go stale. –  Mark Booth Aug 15 '11 at 15:00
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Not this one.. This one is Yahoo answers. YAHOO, seriously. –  John Sonmez Aug 15 '11 at 16:23
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@JohnSonmez I am not sure I would call Yahoo! Answers authoritative. With that said, it is a useful link, +1. –  TimothyAWiseman Nov 16 '11 at 19:21
    
I think that John was being sarcastic. –  Synetech Jul 19 '12 at 18:15

HDD's can still be affected by magnets, but only if you're doing it on purpose. For instance, we had a little hand-held tape degausser (built for VHS tapes) that we would use on HDD's after doing a secure wipe, and before donating them. If the 7-pass bit flipping party wasn't enough, the hand-held degausser probably was - it made the platters vibrate in their casing. I can't imagine that the little bits on each of the platters weren't somewhat disturbed by this violent cataclysm of magnetism. Sure, it's not like the old days when your mom could erase your C64 floppy disk by running the vacuum too close to it on the floor, but the point is you can, you're just not likely to do it on accident. Unless you drop a can of rare-earth bucky-balls on the HDD while it's spinning, or re-enact the laptop destruction scene from Breaking Bad.

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I had a friend who had a bunch of HDDs that he swap in and out like DVDs. One day we were fooling around with some magnetic balls he bought from China and dropped some on two of his HDDs. We figured they were gone but he plugged them in and they were alive and well.

He did some research and learned that this is just a myth because HDDs have very strong magnets inside. I can't copy the text but you can read about it in page 5 of this article = http://www.techarp.com/showarticle.aspx?artno=84&pgno=5

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