What is the theory and concepts use for Magnetic Recording?

Answer 1

Have you ever wondered how a whole album of your favorite music got onto one of those little cassette tapes? Or, what about computer floppy disks; have you ever wondered how they can hold 180 or more pages of typed text? The answer to both of these questions is magnetic recording.

Magnetic recording devices seldom get much attention until they fail to work. But without magnetic recording, recording your favorite television show on a video cassette recorder would be impossible, portable tape players wouldn't exist, and you wouldn't be able to get money from an automated bank teller machine at two o'clock in the morning.

Now what about the Navy? Could it operate without magnetic recording? The answer is definitely no. Without it:

Computer programs and data would have to be stored on either paper cards or on rolls of paper tape. Both of these methods need a lot of storage space, and they take much longer to load into and out of the computer.
There wouldn't be any movies to show or music to play on the ship's entertainment system when the ship is at sea and is out of range for television and radio reception.
Intelligence-collection missions would be impossible since you couldn't store the collected signals for later analysis.
As you can see, magnetic recording plays a very important part both in our Navy life and in our civilian life.

HISTORY OF MAGNETIC RECORDERS

In 1888, Oberlin Smith originated the idea of using permanent magnetic impressions to record sounds. Then in 1900, Vladeniar Poulsen brought Mr. Smith's dream to reality. At the Paris Exposition, he demonstrated a Telegraphone. It was a device that recorded sounds onto a steel wire. Although everyone thought it was a great idea, they didn't think it would succeed since you had to use an earphone to hear what was recorded. It wasn't until 1925, when electronic amplifiers were developed, that magnetic recording started to receive the attention it deserved.
For detailed description:
http://www.aacg.bham.ac.uk/magnetic_materials/magnetic_recording.htm

Answer 2

In a nutshell:

There are tiny clusters of atoms grouped together in magnetic tape called Domains.

The recording head recieves a voltage current from a microphone (air molecules move the diaphram of the microphone creating a disturbance in it's magnetic field, sending current through the wire; for more info look up ADC on google) and directs the 'domains' on the magnetic tape in concurrence with the incoming voltage which literally imprints a proverbial 'picture' of the voltage onto the tape.

This tape can then be played back. The playback head interprets these fluctuations in the domains as a voltage signal (see DAC on google), then acordingly vibrates a speaker cone which moves the surrounding air molecules in a fashion similar to the way the source moved them; thus effectively recreating the sound captured on the magnetic tape.

Hopefully this helps.

Answer 3

Nicholas B talks about a "voltage current."

Make up your mind Nicholas.

Perhaps you should have a talk with your science teacher and get him to explain the difference.