# Magnets and Electronics

**URL:** <https://boards.straightdope.com/t/magnets-and-electronics/265801>\
**Category:** Factual Questions\
**Created:** [September 24, 2004, 1:44am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801 "2004-09-24T01:44:10Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![feppytweed](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/feppytweed/32/4280_2.png) [@feppytweed](https://boards.straightdope.com/u/feppytweed)\
**Post date:** [September 24, 2004, 1:44am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/1 "2004-09-24T01:44:10Z")

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can a neodymium magnet thats the size of a large hockey puck mess up or ruin cd’s or laptops or watches? anything electronic?

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [September 24, 2004, 3:31am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/2 "2004-09-24T03:31:39Z")

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CDs are plastic, so magnets won’t mess them up. Magnetic storage (hard drives, floppies, videotapes, etc) can be hardily screwed by a magnet. Anything with small metal parts (mechanical watches, etc) can potentially get screwed up if the magnet yanks stuff around inside.

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**Author:** ![Nanoda](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Nanoda](https://boards.straightdope.com/u/Nanoda)\
**Post date:** [September 24, 2004, 5:30am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/3 "2004-09-24T05:30:57Z")

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Yeah, any optical media are going to be fine, and I wouldn’t take any great care with my digital watch around a magnet, though if I had a more expensive mechanical one, I’d take note. Certainly touching something metallic on a laptop with something like that could affect the HD inside. If it’s quite strong, you could permenantly mess up your television or CRT.

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [September 24, 2004, 10:38am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/4 "2004-09-24T10:38:07Z")

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Would a hard drive be affected? They are usually shielded aren’t they?

One thing your magnet will screw up is the magnetic strip on credit cards - I discovered this to my cost when I idly put a very powerful magnet (which I took out of an old hard drive) in my pocket.

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**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\
**Post date:** [September 24, 2004, 11:17am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/5 "2004-09-24T11:17:56Z")

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> [@Mangetout](#):
>
> Would a hard drive be affected? They are usually shielded aren’t they?

They aren’t shielded against magnetic fields. That is usually done with Mumetal (5% Copper, 2% Chromium, 77% Nickel, and 16% Iron).

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**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\
**Post date:** [September 24, 2004, 11:27am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/6 "2004-09-24T11:27:52Z")

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> [@Mangetout](#):
>
> Would a hard drive be affected? They are usually shielded aren’t they?

Yes, they’re shielded, but not heavily. You can buy erasers that will wipe out hard drives:

[http://www.datalinksales.com/degaussers/hd1.htm](http://www.datalinksales.com/degaussers/hd1.htm)

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**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\
**Post date:** [September 24, 2004, 11:35am UTC](https://boards.straightdope.com/t/magnets-and-electronics/265801/7 "2004-09-24T11:35:07Z")

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Also note that the eraser I linked to above states a field strength of 4,350 Gauss.

A tiny neodymium magnet can match that:

[http://www.gaussboys.com/product\_info.php?cPath=&products\_id=37](http://www.gaussboys.com/product_info.php?cPath=&products_id=37)