> What I wonder about is what happens when someone turns on a 12 amp vacuum cleaner, a monitor nearby goes into powersaving mode, someone moves their laptop or someone with their own cellphone walks past. These things emit magnetic fields, so I wonder how they've solved the problem of the local deviation changing constantly.
Are any of those magnetic disturbances even within an order of magnitude of a smartphone's compass threshold? I'm surprised that the disturbance from a skyscraper's skeleton would be detectable, and a computer monitor seems like even more of a stretch.
Exactly - the steel everywhere in the infrastructure, buildings, and vehicles messes with the ambient magnetic field so the magnetometer can't consistently get a true field reading.
There are basically two purely EM mechanisms at work for large static fields. First, if the field is big enough, it will saturate components that rely on EM effect to work - these will stop functioning until they are removed from the field. Permanent damage possible if other components behave badly in this situation.
The other thing is if you move in the field you will induce currents on anything like a conductive loop in your device. Damage potential is really dependent on the strength, speed of motion, and how sensitive your device is.
Of course, if you have magnetic materials, mechanical damage is also possible.
I suspect those fishing magnets fall off fast enough you'd have to get it lined up just right to a control board to see any effect, if then.
My Android tablet has a GPS device, which has a user readable magnetic field reader using the GPS Status app available in the Google Play Store.
Up here in Maine, we have a magnetic field of around 53 microteslas, and it peaks around 65 in my house, however, for some reason this morning from about 4:45 am to 6:00 am it was bouncing around randomly from 2000 to 10,000* microtesla.
When I turned on GPS Status, it was reading normal, and after the event, it is still reading normal. But what would cause the magnetic field reader to display such a strong field for almost an hour and a half?
* A crappy fridge magnet is 10 to 15 thousand microtesla
Absolutely. The engineer with the laptop had a brain fade - his area was usually CT.
As magnets have got better control over their fringe fields, the issue has got worse. The field goes from nothing to 3T in a very short distance, so 10+ T/m rate of change is not uncommon.
It's clear some disturbances must be measurable because as I walk around the room, the magnetic field measured by my smartphone constantly changes and since the magnetic field of the Earth is practically uniform over small distances, this must mean the disturbances come from my surroundings.
However, when toggling some apparatuses in my room, nothing happened. My laptop doesn't have a hard drive though, but even only centimetres from it, no change was measurable. Neither did anything happen near my lamps or the AC/DC transformator. The only place I measured a difference (<10%) was on the stove (why yes I'll put my smartphone worth hundreds of euros on a hot stove). However, this faded into the background at a distance of about 10 cm.
There are always side effects, some energy of the magnetic field will dissipate anyway in pieces of metal nearby like housings, screws, rebar in the walls etc.
Magnetic field, ah! Right so, interestingly does that mean a polar shift (that every now and again people rave about) might have larger implications than breaking electronics? Ie massive water loss? I feel like it would depend what the poles look like after the shift, is it likely the field could be weakened or would it just flip? I should probably try learn more about this.
Things such as lifts, vehicles, regularly changing stock levels... Or are these all considered negligible?
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