Light micrograph of a read-write magnetic ferrite head of a 3.5-inch floppy disk drive. We can observe the particles and abrasions on the surface of the head. A spindle motor rotates the disk at high speed (typically 300 RPM), while a actuator, driven by a stepper motor, positions the read/write head through various stop positions (each one defines a track). To write data (in sectors and tracks), current is sent by means of a coil in the magnetic head, the magnetic field (magnetic polarization) of the head aligns the magnetic particles in the contact surface with the disc (a system sensitive to dirt-induced errors), and they encode the data digitally (magnetic encoding process). When reading, the magnetic particles in the disk induce a tiny voltage in the magnetic head coil, converting this electromagnetic pulses to binary data. The maximum transfer rate of 3.5-inch floppy disk, is around 1,000 kilobits/s. Field of view size: 2.97 x 4.45 mm (0.117 x 0.175 in)