Why Are Rubbed Plastic Pieces Attracted to Each Other?

[fiziksfun]

1. I'm doing a lab involving electromagnetic force. In the lab I stroked two pieces of clear plastic that were lying on a table. When I held the two pieces of plastic up in the air near each other, they were attracted to one another.

I don't understand why at all? Any ideas?!
Did I give the plastic a charge when I rubbed it ?! If they're attracted doesn't that mean they have opposite charges ?! Help!

 

[Kurdt]

The plastic will have built up a static charge yes. Since they were attracted the charges will be opposite.