Electric Fields and Plastic Liners
Date: Thursday, November 28, 2002
I have just completed a unit on magnets with my students.
I have been thinking about positive and negative poles. I am curious
about a phenomenon I have noticed. When I dump the chaff from our bird's
used bird food into my trash container - lined with a clear plastic bag -
the chaff will form vertical lines uniform distances apart (I would say
about 1/2 inch apart). Sometimes the bits of chaff will jump from one
location to another but maintain these vertical lines. I thought it was
way cool but did not understand the cause. Can you help me out here?
This sounds like the trash can plastic liner is blow-molded or extruded
polyethylene. Either of these production methods employs various "slip"
additives as processing aids, and these frequently show surface
inhomogeneities in the direction of the process -- hence the parallel lines.
They also can either become electrically charged by static electricity. Your
chaff from the bird feeder, if it is oppositely charged will stick to these
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