 Electromagnetic energy harvesting

Electromagnetic energy harvesting converts mechanical motion into electrical output by changing the magnetic flux through a conducting coil. Relative motion of a magnet and coil induces an electromotive force according to Faraday's law of induction. With a load connected, a current flows and transfers energy to the circuit.

A hand-driven magnet moving through a coil gives a direct demonstration: faster motion changes the flux more rapidly and usually produces a larger induced voltage for the same path. The current's magnetic response opposes the driving change, as expressed by Lenz's law. Mechanical work against that response supplies the electrical output. Coil resistance produces heating, and mechanical friction adds further losses; an unloaded voltage measurement alone does not measure the energy the device can deliver.