Ok say I have and acetate rod and rub it with a cloth leaving it with a positive charge. I can then use this rod to attract pieces of paper which are neutral.

But why does this happen because if the paper is neutral then the attraction and repulsion forces will be equal so surely the paper wouldn't move at all

:bugeye: hmmmmmmmmmmmmmmmmmm.

Originally posted by BobG
But why does this happen because if the paper is neutral then the attraction and repulsion forces will be equal so surely the paper wouldn't move at all
The paper is composed of lots of positive particles (nuclei) and negative particles (electrons). Even if it is on the whole electrically neutral, it still contains components of both charges.

When you put the piece of paper in an electric field (by bringing the acetate rod near it), you encourage all of the positive charges in it to lean a bit to one side, and all of the negatives to lean a bit to the other. It is said that you induce a dipole moment in the paper by encouraging the charges to separate slightly with an electric field.

Then the charge on the nearest side experiences a greater attraction to the rod than the repulsion experiences by the equal charge on the far side. The paper is then, on the whole, attracted to the rod.

- Warren

nothin' like a good ol' dipole inducement moment ....:D

Originally posted by pumpkinsaren'torange
nothin' like a good ol' dipole inducement moment ....:D
"induced dipole moment," please. ;)

- Warren