So I just started Physics 2 Electricity and Magnetism and I'm already scared for my life. The professor first did a demonstration where he charged up a Teflon rod on some sort of cloth and moved an aluminium can with the rod. I understand how that happens. The can is a metal and conductor so the electrons are relatively free to move around, so all the electrons go to one side of the can and the other side is positively charged so the can moved because of this polarization effect. What I did not understand was the next demonstration where he charged the same rod and moved a piece of wood (which was balanced on a pivot). I did not expect that because I thought wood was an insulator and thus the electrons are not free to move around and no polarization occurs. Can somebody explain why this happens?