You've probably magnetized lots of stuff before those
paper clips. Ever tape record
someone talking, or record a TV program on your VCR?
Magnetic tapes, like the ones you put in your tape player and your VCR, write
the music by magnetizing small parts of the tape. The disk drives and floppy
drives in your computer also magnetize small dots to store your files.
Don't bring your magnet near your tapes or floppies! It can erase them.
Don't even think about erasing anybody else's floppies. It's a mean idea, and
only pinheads would do it.
As you crumple a piece of paper, little areas bend and crackle. In the
same way, as you magnetize a magnet, little areas of the magnet
become magnetized. As these areas jump from one magnetization to another,
they make crackling noise!
If areas jump from one magnetization to another, then the tape recorder
can't record perfectly: it can only get within one jump of the right value.
(It's like drawing with a pencil on the sidewalk: you try to draw a straight line,
but it comes out bumpy when you hit all the little pebbles and grains in the cement.)
Experiment: Hiss on Audio Tapes.
If you have a boom box and a blank tape, you can hear
the problem caused by the jumps in the magnetization. Put the blank tape
into the tape deck, and slowly turn up the volume until you hear a hiss. You can
tell the hiss is on the tape if it gets louder and softer as you push the
volume up and down.
Be careful to turn down the volume again when you're done! The next person could
ruin both the speakers and her ears. The next person could be you!