Friction Electricity

We know that opposite charges attract,

and that like charges repel,


Those are easy to understand. However, we also find that a charged object is attracted to an uncharged object (such as your finger)!

How can this be?

What is happening?

Even tho' your finger has no net electric charge, it certainly has lots(!) of electric charges. Because of the presence of the additional charged object, these charges can move around. This is called charge polarization. Even in an insulator, where electrons can not easily flow, they can move from one side of an atom or molecule to the other.

If we bring a conductor close to the charged object, electric charges can flow from one part of it to another,

Because of this charge polarization, a charged object will be attracted to a neutral or uncharged object. That also means that this attraction may dominate or be seen instead of a very small repulsion between two charged objects if one has a much greater charge than the other.

Electric Fields and Conductors

Electric Potential Energy

Return to Ch 17, Electrostatics & Electric Energy
(c) Doug Davis, 2002; all rights reserved