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Magnetic Recording/Audiocassette

The Discovery Of Electromagnetism, Recording On Tape With An Electromagnet, Operation Of The Playback Head

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.


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Science EncyclopediaScience & Philosophy: Macrofauna to Mathematics