Transformers and other applications

Induction does not only produce current: it also transforms it and transmits it without contact. The major example is the transformer. Two coils share the same iron core. An alternating current in the first creates a varying flux; this varying flux, crossing the second coil, induces a voltage there. No electrical connection between the two — only the magnetic flux links them.

   coil 1 (N₁ turns)  ~~~ iron core ~~~  coil 2 (N₂ turns)
   voltage U₁         varying flux        voltage U₂
                U₂ / U₁ = N₂ / N₁     (the turns ratio sets the voltage)

By choosing the number of turns, you step up or step down the voltage. This is essential to the grid: electricity is carried at very high voltage (fewer losses over long distances), then stepped down near homes. Without transformers, no modern grid.

Contactless induction is everywhere else:

   induction hob       ->  a varying field heats the pan directly
   wireless charger    ->  recharges a phone without wires
   RFID badge / card    ->  the reader powers the chip from a distance
   bike dynamo          ->  lights the lamp as you pedal

Each time, the same principle: a changing magnetic field induces a current or a voltage at a distance. From the power plant to the wireless charger, Faraday's law works away, discreet but ubiquitous, in almost every device around us.