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Name: Loretta
Status: educator
Age: 40s
Location: N/A
Country: N/A
Date: Thursday, November 28, 2002
Question:
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?

Replies:
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 tracks.

Vince Calder


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