Barkhausen Effect (J3) [5G20.10]
A soft iron core is placed inside a solenoid having several hundred turns of fine wire. The coil winding is connected to a loudspeaker. Audible results of the Barkhausen Effect are produced by slowly moving a permanent magnet toward the solenoid core. A loud rasping sound will be heard caused by the domains aligning themselves. Successive passes produce no sound until the polarity of the magnet is changed.