# How careful do I have to be with magnets around my stuff? **URL:** \ **Category:** Factual Questions\ **Created:** [October 1, 2008, 7:20pm UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048 "2008-10-01T19:20:23Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [October 1, 2008, 7:20pm UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/1 "2008-10-01T19:20:23Z")
I recently bought some neodymium magnets for Dominic for his birthday (man are they cool to play with!) and I’m not sure what all they could affect. I know not to put them near a monitor or TV screen, and obviously not near a floppy disc. How about my laptop? Are there areas on that that could be affected by these things? What about my cell phone? Digital camera (SD card)? Anything else I should be careful about? ---
**Author:** ![Superfluous\_Parentheses](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@Superfluous\_Parentheses](https://boards.straightdope.com/u/Superfluous_Parentheses)\ **Post date:** [October 1, 2008, 7:22pm UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/2 "2008-10-01T19:22:32Z")
Be careful with credit or debit cards with magnetic strips. ---
**Author:** ![Don\_t\_Call\_Me\_Shirley](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@Don\_t\_Call\_Me\_Shirley](https://boards.straightdope.com/u/Don_t_Call_Me_Shirley)\ **Post date:** [October 1, 2008, 7:41pm UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/3 "2008-10-01T19:41:57Z")
> [@OpalCat](#): > > I recently bought some neodymium magnets for Dominic for his birthday (man are they cool to play with!) and I’m not sure what all they could affect. I know not to put them near a monitor or TV screen, and obviously not near a floppy disc. How about my laptop? Are there areas on that that could be affected by these things? What about my cell phone? Digital camera (SD card)? Anything else I should be careful about? I don’t know how old Dominic is, but if there’s any chance he could swallow them you should keep them away from him. Swallowing more than one can be very dangerous. Also, if they are not coated with plastic or something they are very breakable and when they break they have very sharp points. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [October 1, 2008, 9:03pm UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/4 "2008-10-01T21:03:25Z")
1. If they’re strong enough (and particularly if they’re not round), if you’re not careful handling them they can give your finger or other body part a wicked pinch as they come together. 2. Probably obvious, but keep them away from any kind of swipe card (employee ID badge, hotel room keycard, subway fare card). Some kinds of card might survive, but better not to take the chance. 3. What better time to finally say hi? ---
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [October 2, 2008, 2:59am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/5 "2008-10-02T02:59:37Z")
> [@Don\_t\_Call\_Me\_Shirley](#): > > I don’t know how old Dominic is, but if there’s any chance he could swallow them you should keep them away from him. Swallowing more than one can be very dangerous. Also, if they are not coated with plastic or something they are very breakable and when they break they have very sharp points. He’s 13, so I don’t think that’s a problem. ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [October 2, 2008, 3:10am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/6 "2008-10-02T03:10:02Z")
Keep them away from laptops and computers to avoid rewriting your hard disks. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 2, 2008, 3:35am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/7 "2008-10-02T03:35:53Z")
> [@The\_Second\_Stone](#): > > Keep them away from laptops and computers to avoid rewriting your hard disks. Not gonna happen. For one thing, inside every hard drive is a pair of magnets far stronger than those typically available to consumers that are used to drive the head arm coil. For another, it takes a very intense magnetic field to write or erase HD data; since magnetic field strength drops off with the cube of the distance, hard drive heads only manage it because they float mere microns above the platter surface. A magnet powerful enough to do the job from outside the HD enclosure would be extremely dangerous to play with since getting your hand between it and a ferromagnetic surface is sure path to smashed bones. ---
**Author:** ![WolfpackJeep](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpackjeep/32/2921_2.png) [@WolfpackJeep](https://boards.straightdope.com/u/WolfpackJeep)\ **Post date:** [October 2, 2008, 4:08am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/8 "2008-10-02T04:08:30Z")
Do you have a cell phone with a large screen and/or touchscreen on the outside? Keep the magnets away from those. The phone itself will be OK, but the screen could develop dark patches if exposed to the magnets for long periods of time. ---
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [October 2, 2008, 4:12am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/9 "2008-10-02T04:12:18Z")
> [@WolfpackJeep](#): > > Do you have a cell phone with a large screen and/or touchscreen on the outside? Keep the magnets away from those. The phone itself will be OK, but the screen could develop dark patches if exposed to the magnets for long periods of time. Yeah, I do. So I’ve read conflicting evidence online–SD cards… erasable with a magnet or not? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 2, 2008, 4:13am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/10 "2008-10-02T04:13:54Z")
> [@WolfpackJeep](#): > > The phone itself will be OK, but the screen could develop dark patches if exposed to the magnets for long periods of time. I don’t think so. You have a cite for this? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 2, 2008, 4:14am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/11 "2008-10-02T04:14:59Z")
> [@OpalCat](#): > > YSo I’ve read conflicting evidence online–SD cards… erasable with a magnet or not? Not. ---
**Author:** ![FlyingRamenMonster](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@FlyingRamenMonster](https://boards.straightdope.com/u/FlyingRamenMonster)\ **Post date:** [October 2, 2008, 5:04am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/12 "2008-10-02T05:04:13Z")
I think you should just get him to keep them away from anything technological. Not everything is vulnerable to magnets, but it’s easier than remembering which things are safe and which things aren’t. ---
**Author:** ![Mbossa](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@Mbossa](https://boards.straightdope.com/u/Mbossa)\ **Post date:** [October 2, 2008, 5:10am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/13 "2008-10-02T05:10:27Z")
Know anyone with a pacemaker? Probably best to keep magnets away from those. ---
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [October 2, 2008, 5:54am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/14 "2008-10-02T05:54:12Z")
> [@FlyingRamenMonster](#): > > I think you should just get him to keep them away from anything technological. Not everything is vulnerable to magnets, but it’s easier than remembering which things are safe and which things aren’t. Well it isn’t just an issue of him keeping them away from stuff. I got some for the house in general as well (they kick ass at holding papers onto the fridge) and they’re just impossible not to play with. So it’s all of us doing the fiddling, and you’ll be messing around with them, and put one on your lap and then realize “oh shit! my cell phone is in my pocket! I hope I didn’t screw anything up…” That kind of thing. None of us would intentionally put them near electronics, but I just want to know exactly what the risk is to different things so I know what stuff to be hyper-careful about and what stuff I don’t need to give myself massive anxiety over. 🙂 ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 2, 2008, 6:01am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/15 "2008-10-02T06:01:08Z")
It’s often not noticed, but there is a surprising amount of electronic circuitry in a modern kitchen. Microwaves, automated coffee makers, blenders, food processors, toaster ovens, etc. often have electronic parts, that could possibly be damaged by these magnets. And many of those are pretty expensive! So keep that in mind if he’s in the kitchen. Also, some wristwatches may be vulnerable. ---
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [October 2, 2008, 6:21am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/16 "2008-10-02T06:21:23Z")
(Also, how far away from something is considered “safe”? I know they don’t have a very long range, but I don’t know how far away is “for sure safe” from harm… it’s these specifically, by the way: [http://www.teachersource.com/ElectricityAndMagnetism/NeodymiumMagnets/Gold\_CoatedNeodymiumCubes\_10pk.aspx](http://www.teachersource.com/ElectricityAndMagnetism/NeodymiumMagnets/Gold_CoatedNeodymiumCubes_10pk.aspx) ) ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 2, 2008, 11:01am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/17 "2008-10-02T11:01:29Z")
> [@t-bonham@scc.net](#): > > It’s often not noticed, but there is a surprising amount of electronic circuitry in a modern kitchen. Microwaves, automated coffee makers, blenders, food processors, toaster ovens, etc. often have electronic parts, that could possibly be damaged by these magnets. And many of those are pretty expensive! So keep that in mind if he’s in the kitchen. No. Solid state electronics are not affected by ordinary magnetic field strengths. Unless you have an MRI in your kitchen, you have nothing to worry about. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [October 2, 2008, 11:46am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/18 "2008-10-02T11:46:48Z")
**QED** writes: > [@](#): > > Not. I have to ask – cite? The reason I ask is that someione recently told me that you’d need a strong neodymium magnet (which is precisely what we’re talking about) to erase a magnetic strip on a card, citing Mythbusters. But our ouwn Cecil much earlier cited a Citibank report saying that the magnets in one of those notorious eelskin wallets could erase the magnetic strip on a band card from _2 inches away_ (!!): [http://www.straightdope.com/columns/...k-teller-cards](http://www.straightdope.com/columns/...k-teller-cards) I found this such a considerable discrepancy that I started a thread in Comments on Cecil’s Columns just a couple of days ago – was this an unusually powerful magnet in that particular wallet, or did the Mythbusters use a particularly weak one, or what? I haven’t received a useful answer yet > **[Eelskin Wallets](https://boards.straightdope.com/sdmb/showthread.php?t=485694)** > > I mentioned the findings in Cecil’s column on eelskin wallets to a co-worker (the column is here: Do eelskin wallets demagnetize bank teller cards? - The Straight Dope) Aha! Tested by actual experiment! My co-worker replied that Mythbusters had... ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [October 2, 2008, 11:50am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/19 "2008-10-02T11:50:50Z")
Here’s what I’d make. I’ve been wanting to do this for about a year. The Gauss Rifle: A Magnetic Linear Accelerator > **[Chapter 1: Magnetism -- Build a Gauss Rifle magnetic linear accelerator](https://sci-toys.com/scitoys/scitoys/magnets/gauss.html)** > > Make a gauss rifle -- a magnetic linear accelerator ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [October 2, 2008, 11:54am UTC](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048/20 "2008-10-02T11:54:44Z")
> [@CalMeacham](#): > > I have to ask – cite? > The reason I ask is that someione recently told me that you’d need a strong neodymium magnet (which is precisely what we’re talking about) to erase a magnetic strip on a card… QED was responding to the question about erasing an SD card. This is not a device that employs magnetism, and thus the data it contains would not be affected by a magnetic field. The same would be true of nearly all PC memory cards and “thumb drives” currently popular. [Next page](https://boards.straightdope.com/t/how-careful-do-i-have-to-be-with-magnets-around-my-stuff/466048.md?page=2)