# Question #0b8e1

The induction only happens because there are 6 little magnets in the pickup and the strings are partially magnetised as a result. Motion of a magnet (the string) causes a changing magnetic field and any conductor in a changing magnetic field will have a current induced in it. The equation linking the change in magnetic field (or more correctly, flux) and the potential difference, $\epsilon$ is Faraday’s law, $\epsilon = - N . \frac{\mathrm{dp} h i}{\mathrm{dt}}$ where N is the number of turns in the coil.