Magnetic Data Storage Help
Magnetic fields can be used to store data in various forms. Common media for data storage include magnetic tape and the magnetic disk .
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.
The era of the personal computer has seen the development of ever-more-compact data storage systems. One of the most versatile is the magnetic disk. Such a disk can be either rigid or flexible. Disks are available in various sizes. Hard disks (also called hard drives) store the most data and generally are found inside computer units. Diskettes are usually 3.5 inches (8.9 cm) in diameter and can be inserted and removed from digital recording/playback machines called disk drives .
The principle of the magnetic disk, on the micro scale, is the same as that of magnetic tape. But disk data is stored in binary form; that is, there are only two different ways that the particles are magnetized. This results in almost perfect, error-free storage. On a larger scale, the disk works differently than tape because of the difference in geometry. On a tape, the information is spread out over a long span, and some bits of data are far away from others. On a disk, no two bits are ever farther apart than the diameter of the disk. Therefore, data can be transferred to or from a disk more rapidly than is possible with tape.
A typical diskette can store an amount of digital information equivalent to a short novel. Specialized high-capacity diskettes can store the equivalent of hundreds of long novels or even a complete encyclopedia.
The same precautions should be observed when handling and storing magnetic disks as are necessary with magnetic tape.
Practice problems of these concepts can be found at: Magnetism Practice Test
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