Respuesta :
The answer is D; the movement of the magnet relative to the coil. In 1831 Faraday discovered magneto-electric induction: the production of a steady electric current. He attached two wires through a sliding contact to a copper disc and by rotating the disc between the poles of a horseshoe magnet, he obtained a continuous direct current creating the first generator. Therefore; whenever the number of magnetic lines of force or magnetic flux passing through a circuit changes and emf is produced (induced emf).