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Before I begin, anyone here who dislikes me - I'm asking this question because my common sense dictates that it should'nt be so. I'm not here to troll, stir shit or pass judgment on any users on this site. I ask that before I get the usual knee-jerk reactions read the post and if you have an answer then post away otherwise, take a deep breath and move on. And yes I have posted this as 'residue'.

I saw an ad for the Logitech Case + Drive in a tech mag recently.



So clearly the iphone cover has a ferrous case.
My question is this - I have always been told and adhered to the rule that electronics (basically anything with a pcb) and magnetic fields don't mix. As far as I'm concerned that's a pretty fundamental rule.
Yet here they have an obviously ferrous cover (if it was aluminum for example it wouldn't stick to the magnet) being placed in a fairly strong magnetic field - strong enough to hold it in place in a moving vehicle. Now I know that no matter how long you hold a piece of iron next to a magnet it won't magnetize. Wipe it across that magnet and you've got an instant magnet. Primary school science right?

So surely a ferrous covered phone with highly conductive and ferrous based metals inside it being repeatedly taken on and off it's magnetic "cradle" would be asking for some sort of hardware problems eventually? Particularly with constant use.

Am I getting it wrong somewhere? Is my science out of whack here?
FTR I don't own an iphone and I don't use my phone when I'm driving - I've got one of those bluetooth dongles but tbh my phone is rarely on any setting apart from "silent".

I can see what'd give that impression, but magnets were only really important in a couple of cases:
- Magnetic storage (floppies) - smartphones use flash memory now, unaffected.
- Cathode ray screens (remember how speakers placed next to a screen started warping the colors?) - again, LCD is unaffected.

I'm unsure what kind of loudspeaker is in it, and the coil in that might be affected, but probably not permanently.

Yeah, dont mix up static magnetism with induction which can indeed damage circuits due to overload.

Smartphones have a magnetic field sensor. I wonder it that could be affected.

The compass might be depending on the magnet size.

^ That's my point tho - it's the moving the phone to and fro on and off the cradle rather than it just sitting next to the magnet that I was wondering about. As I mentioned - stroke a magnet across metal and you'll magnetise the metal (eventually). But isn't solder ferrous? And therefore susceptible to being magnetised by a regular "swiping" movement say or the slight movement of the phone on the cradle as you drive?
I'm sure I'm wrong - they wouldn't sell something as dodgy as what I'm suggesting.. would they?

Hard to tell - in any case they've been selling magnetized phone cases for a while now, weren't they?

maybe its a special healthy kind of magnetism invented by apple? ;P

^Clearly doesn't fix pancreatic cancer. Too soon?

I know people who've used cases with magnets for quite a while (they're popular with some photography people, as you can get magnetically mounted lenses for the camera) without any issues.

That one has a big red "is this really a good idea?" warning for me though: it's a car dashboard mounting aid. Why would you use that? For GPS. Which is probably the no.1 time where you want the compass in the phone to work, so you know which direction you're facing (that gets determined from motion, but only once you're moving). Is the compass going to be accurate that close to a magnet?

Then again I've rarely seen any compass work reliably in a car, especially next to the dashboard. There's just too many sources of magnetism and/or induction around.

Probably so. Well, how about we just assume it's not safe to use a phone in a car at all? :)