can a neodymium magnet thats the size of a large hockey puck mess up or ruin cd’s or laptops or watches? anything electronic?
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.
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.
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.
They aren’t shielded against magnetic fields. That is usually done with Mumetal (5% Copper, 2% Chromium, 77% Nickel, and 16% Iron).
Yes, they’re shielded, but not heavily. You can buy erasers that will wipe out hard drives:
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