= 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.
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