Everyone has tried to levitate an object using a fridge magnet. After a few half-hearted attempts you realize that, though possible in theory, it is not possible in practice. If you get ever so slightly too close to the magnet, the magnetic field becomes ever so slightly stronger and the object goes flying towards the magnet until *clack* and it’s stuck like barnacle. Likewise, if you get ever so slightly too far from the magnet, the magnetic field becomes ever so slightly weaker, and earth’s gravity claims another victim.
This is what we engineers would call an unstable system. Although an unstable equilibrium exists (a theoretical position where the weight of the ball and the pull force of the magnet are equal), it is not robust to disturbances. So, the challenge is to MAKE the system stable, by giving the magnet a “brain” of sorts. We call this “brain”, which is just a carefully designed circuit, the “controller”. A magnet with the properly designed controller will be able to REDUCE its strength if our levitating object gets too close and INCREASE its strength if our levitating object gets too far.
2 weeks later, we have physical evidence that Maglev trains are a stupidly impractical idea (the sheer amount of current we needed just to make a 16 g ball float was enough to kill an elephant).
Stay tuned for updates to this post which will go into technical details!
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