why shouldn't magnets be brought near tv's, radios, computers, etc.

Dear Student,

The magnetic field produced by the magnet will affect the CRT based TV and computer monitors. The monitors and TVs use a metal plate at the front of the picture tube, to focus electron beams from the electron gun. This plate is known as shadow mask. When this plate got magnetized from external magnetic fields, it produces discolouration at that point. The introduction of magnets near the radio receivers may increase the noise of the radio.

Regards