Every time I hear the description of a wireless charging system it goes like this: "remember a transformer? It's the same here – one coil is in the base and another is in the device and when you put the device onto the base the transformer gets assembled and starts transmitting power".
One problem with this description is there's no magnetic core in the system. AFAIK each transformer has a magnetic core in its design. A magnetic core is a huge set of steel plates that goes though both coils and this set of plates in fact conducts energy – the alternating current in the primary coil induces alternating electromagnetic field in the core and that field induces current in the secondary coil.
So looks like the core is a key component and a transformer can't possibly work without a core. Yet I don't see a magnetic core in a wireless charging system.
How does it work without a magnetic core?