Magnetic Recording/Audiocassette

Audiocassette tape recorders are widely used to record and play back music or speech. Information is stored on a narrow ribbon of plastic tape that has one side coated with a magnetic material, such as iron oxide. An electromagnet aligns individual magnetic particles in a pattern that corresponds to the loudness and frequency of incoming sounds. In order to play back the recorded information, the magnetic tape moves past a pickup coil that generates an electrical output signal. After being amplified, this signal causes a speaker to vibrate which produces sound waves for the listener. A tape recording can be erased by using a rapidly changing magnetic field that scrambles previously recorded patterns of particle alignment.