So magnet is not safe?

Recently there is a bit of chaos when some famous smartphone manufacturers begin placing some magnet to their phones so that accessories can be attached to easily without further effort. So as it seems that static magnetic solution is the best. However, concern grows about the potential hazard poised by these magnets to electronic devices namely the medical devices i.e. pacemaker. So how safe is this magnet thingy?

To be able to answer this thoughtfully and scientifically, we have to go back to basic i.e. electromagnetic theory. First we need to distinguish between magnetic field vs electric field vs electromagnetic field vs static field vs time-varying field. Yes, there are many of them. Magnetic field produced by a magnet is a static magnetic field i.e. field does not vary with time. Remember this is as the important bit. Apart from attracting ferrous materials (or anything that operates under static magnetic field such as motor, solenoid etc), basically it does nothing if left alone. Now here is the caveat. The static magnetic field becomes problematic when the magnetic field (or flux) becomes time-varying. The time-varying magnetic flux, when it passes through a loop of wire (hereby circuits, PCB tracks, solenoids etc) produces current in the loop. This current is an ‘extra’ in the system that the system may not recognise (or cannot handle) hence causing wrongful operation.

So when does the static magnetic field become time varying? Very easily. When you are moving the magnet, the so-called victim ‘saw’ a changing field due to the moving magnet. The magnitude of the field becomes smaller as you move further away and vice versa. Such behaviour is inducing current in the victims. As a result, when you are placing a magnet near to a medical device (or whatever electronics that you are using) on your body, the act of walking, moving, and running, will cause the distance between the devices and the magnet to vary. From what I have explained above, it may cause problems.

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