Electricity and magnetism are endlessly fascinating. And this is such an amazing demonstration because the result is so unexpected. It even amazes all the smart students at the University of Calgary!
I started with a standard cable used to connect an mp3 player to a small powered speaker. And then I cut that cable in half. To each of the cut ends, I attached a wire loop with about 50 turns. When the mp3 player is turned on and the loops are brought close to each other, music pours out of the speaker!
The technical term for this is 'inductive coupling'. The mp3 player sends an electric current into the speaker wire. As the current flows through the coi
l, it generates a magnetic field. When the second loop is brought close to the first one, the magnetic field induces the same electric current in the second loop. This in turn produces sound from the speaker.
This is the principle employed to keep an electric toothbrush charged with one of those sealed base units!
As I am fond of saying, electricity and magnetism are just two sides of the same coin. You can't have one without the other!