flash memory is used in the devices that you listed, eg, phones. so
obviously, it wont be erased because of that.

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> Is flash memory (like in SD,CF,SMC,etc. cards) magnetic?
> How close to a magnetic source would it have to get to be damaged. This
> hasn't happened to me yet personally, but what if it's laying on the floor
> and somebody vacuums right next to it. That'd be a 10 amp motor right
> next to it. What about the old laying it on top of your monitor or phone
> thing, like used to happen back in floppy days?
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Flash memory uses capacitance not magnetism. As far as I know its
impervious to most normal external electromagnetic raditation. You
pretty much have to be in the circuit to change the voltage in the
flash memory cells. The following is lousy physics, but I've tried to
explain it as best I can. Both flash and magnetic storage are based on
storing electrons. Magnetic memory is coerced (induced) into arranging
electrons on the media a particular way through the electromagnetic
fields generated by the by the recording heads. This arrangement of
electrons gives the media the electromagnetic characteristics that
allow the heads to identify data correctly when reading it. Strong
external magnetic fields can also re-arrange the electrons, making them
non-sensical to disk drive heads. Flash on the other hand is
implemented as tiny capacitors in integrated circuits where electrons
are deposited directly on whatever passes for capacitor plates in the
silicon realm. The electrons stored are not in any particular
arrangement, they are simply "piled up" there and once they are piled
up, there is nowhere else for them to go until the circuit creates an
inverse operation and drains them away. I think you could probably
place flash memories in a cat scan (much less next to an industrial
strength electric motor) and they would retain their data. No - I
certainly haven't tried cat-scanning and don't advocate sneaking one in
to check it out. I'm sure there are materials engineers and the like
who could tell you what the tolerances are of these circuits to all
kinds of EMI. Accidental or intentional microwaving does not qualify as
a best practice. One last serious point - flash does wear out - the
last time I checked it was around every million writes or so. OK for
data archiving, perhaps a bit risky for transaction processing.