how can a recorder record

[Melissa_dwl]

how does a tape(the magnetism) work

[smorodina]

I'm surprised nobody has answered this, so I'll have a go, although it's a bit complex to answer in detail. The tape is a ribbon of plastic with a coating of a metalic based substance on it (ferric oxide on standard tapes). This is sensitive to magnetic fields in the same way as iron filings will form a pattern when near a magnet. The 'head' of the tape recorder is an electro-magnet, and the field of the magnet varies according to the waveform of the sound fed to it from the recorder. As the tape moves over the head, a varying pattern of magnetism is formed on the coating which matched the waveform of the source. On replay, the head responds to the magnetic pattern and feeds a waveform back into the playback circuitry of the recorder and thus the sound is re-created. I hope that is reasonably clear?

[voan2]

so why can a varying pattern of magnetism record sound?

[smorodina]

Sound is a series of vibrations of the air. When these vibrations hit the diaphragm of a microphone they induce a tiny electric current (without going deeper into electronics) which is amplified by the circuit of the tape recorder. The fluctuations of this electric signal follow the pattern of the original sound wave. If this signal is fed through a circuit designed to drive a speaker, the speaker will vibrate in the same way as the original sound, causing an air disturbance which recreates the original sound. If the voltage is sent to a tape head, it causes varying magnetism to be recorded on a tape which also follows the varying levels of the original sound, but there is no sound recorded on the tape. It is just a pattern which represents the sound. When the process is reversed, the magnetic pattern causes an electric current in the tape player which follows the fluctuations of the original sound to be generated, and this can be fed back to the speakers, where it again recreates the original sound. Difficult to explain, but it works!