Fundamental Knowledge about Electromagnetism

Faraday's Law

"Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc."

How USB charging works, or how to avoid blowing up your smartphone

"The tech world has finally coalesced around a charging standard, after years of proprietary adapters and ugly wall wart power supplies. Well, sort of: We’re already seeing some fragmentation in terms of the new USB-C connector, which could eventually replace USB, as well as what is thankfully turning out to be a short-lived obsession Samsung had with larger USB Micro-B connectors for its Galaxy line. But aside from that, and with the obvious exception of Apple’s Lightning connector, micro USB has destroyed the industry’s penchant for custom ports.