We know that with each passing day, new technological equipment appears, willing to make our daily life viable. Today, to listen to music, just plug a headset into your cell phone. It is also possible to use the so-called iPods, which have a large space for music storage.
If we ask our parents which device they used to listen to music on, they will surely say cassette players. It is very rare nowadays to find this type of device, which uses K7 tapes. Another device that uses K7 tapes is the VCR, a device now replaced by DVD and Blu Ray.
K7 tape, also called magnetic tape, was used because it was considered one of the most viable ways, ie, the cheapest, to store information. This information could be text, photographs and sounds. Magnetic recording technology was used in K7 tape recorders, floppy disks, hard drives and magnetic cards, better known as credit cards.
Cassette tapes (K7) have a very thin layer of magnetic particles formed by the elements. Faith2O3 or Cr2O3, with the purpose of storing the information, recorded in them, in the form of magnetized regions. Magnetic particles are very small in size, just a few micrometers, and consist of a few magnetic domains.
Magnetic particles, when placed in a thin layer of plastic or polyester, on the magnetic tape, maintain a defined position. If we look at a computer hard drive, we will notice that the magnetic layer is on top of a metal hard drive and that it spins at high speed when turned on.
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Information is recorded as a sequence of well-defined regions on the magnetic layer. After being recorded, the information can be retrieved and transformed into electrical signals, by the microphone, through a sensor that reads the magnetized regions.
After being recorded, we can play the K7 tape just by running it at a constant speed in the read head. The electrical signal that is transformed is amplified and sent to the speakers, which reproduce the sound that was recorded on the tape. Thus, an analog electrical signal can be magnetically encoded, making the strength of the tape's magnetization proportional to the strength of the signal.
The tape, when passing through the magnetic recording system, with constant speed, can become more or less magnetized, depending on the strength of the signal emitted at the time. Once recorded, the tape does not lose magnetization and can be used to reproduce the electrical signal if it is passed at the same speed through a reading system.
By Domitiano Marques
Graduated in Physics
Brazil School Team
Would you like to reference this text in a school or academic work? Look:
SILVA, Domitiano Correa Marques da. "Magnetic tapes"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/fitas-magneticas.htm. Accessed on June 27, 2021.
