Movement of Domains in a Magnetic Material

EQUIPMENT
    Amplifier
    Speakers
    Coil
    Thin Metal Strips  (Al,Cu,Pb,Fe in green box)
    Nails
    Magnet


NARRATIVE
         The movement of domains in a magnetic material generates magnetic fields around them. These may be detected by a magnetic pickup coil and amplified to produce an audio signal.

        Hook up the coil thru the amplifier as you would the microphone. Insert strips of metal (Al, Cu, Pb, Fe) into the coil. Bring a horseshoe magnet near the coil to align the domains. Only the iron strip will render an effect. As the magnet is rotated around the coil with the iron inserted, the domains realign themselves producing a magnetic field.