This is a project that is based on devices that generate electircity
The cards contain a band of magnetic material, which varies like a bar code. The reader is able to sense the variations - similar to the way a hard drive reads magnetic regions. Both probably use hall-effect sensors ( a semiconductor device) rather than a coil of wire around a magnet type of sensor. The hall effect devices would be smaller and have less inductive lag edit. True, hall effect devices don't generate electricity. they detect magnetic fields.
Faraday's law. Hall effect devices don't generate electricity. Changing magnetic flux through a coil does.
