Why should magnets be kept away from cassettes,CDs, mobile, tv, plastic cards etc.?
Presence of Magnets will not affect CDs which are optical in nature. But magnetic tapes i.e. cassettes contains celluloid films coated with ferromagnetic substances. These magnetic tapes contain the audio signal as a varying magnetization of the magnetic material. So if it be exposed to a magnet, it may loss the data. Magnets before a CRT TV will deflect the electron beams improperly and that will lead to color disturbances. Mobiles contain hard disk which are again magnetic means of data storage, thus data loss may occur, plastic cards contain magnetic strip for data storage thus presence of magnet may impair the data in the card. Above all strong magnets may induce self induction and unnecessary sparks that may impair the electric/electronic devices.