MAGNETIC TAPE

Recording tape is the stuff you find in cassette players. These days, magnetic tape is largely obsolete, but it is still sometimes used for home entertainment, especially high-fidelity (hi-fi) music and home video. It also can be found in some high-capacity computer data storage systems.
The tape consists of millions of particles of iron oxide attached to a plastic or nonferromagnetic metal strip. A fluctuating magnetic field, produced by the recording head, polarizes these particles. As the field changes in strength next to the recording head, the tape passes by at a constant, controlled speed. This produces regions in which the iron oxide particles are polarized in either direction. When the tape is run at the same speed through the recorder in the playback mode, the magnetic fields around the individual particles cause a fluctuating field that is detected by a pickup head. This field has the same pattern of variations as the original field from the recording head.
Magnetic tape is available in various widths and thicknesses for different applications. Thick-tape cassettes don’t play as long as thin-tape ones, but the thicker tape is more resistant to stretching. The speed of the tape determines the fidelity of the recording. Higher speeds are preferred for music and video and lower speeds for voice.
The data on a magnetic tape can be distorted or erased by external magnetic fields. Therefore, tapes should be protected from such fields. Keep magnetic tape away from permanent magnets or electromagnets. Extreme heat also can damage the data on magnetic tape, and if the temperature is high enough, physical damage occurs as well.