# Electrostatics (conduction) and polarization.

1. Aug 30, 2009

### ThetaPi

1. The problem statement, all variables and given/known data

Describe how a metal sphere on an insulating stand is charged if a positively-charged rod were to touch the sphere. (This is a 5 mark problem, so at least 5 major points should be included in the answer. I am not sure whether I have fully answered the problem.)

2. Relevant equations

Not applicable, of course.

3. The attempt at a solution

The electric charge is created by conduction (charging by contact). When the positively-charged rod touches the sphere, some of the positive charge from the rod spreads onto the metal sphere because like charges repel one another. When the rod is removed, the positive charge spreads evenly over the metal sphere and remains there since the insulating stand prevents the flow of the charge to the ground. The positively-charged rod has given the sphere a positive charge.

I have another problem which I have no idea as to how to solve it:

1. The problem statement, all variables and given/known data

A positively-charged balloon will stick to a wooden wall by polarizing molecules in the wooden wall to create an oppositely-charged surface. Describe how the charges are aligned on both the balloon and the wall. (This is a three-mark problem.)

Last edited: Aug 30, 2009
2. Aug 30, 2009

### Chi Meson

As a teacher, I would not yet give you full points for this answer. Remember, this is a solid conductor. Think of the actual particles that are moving about and carrying the charge from one object to the other? What are they called, and which way do they actually move?

3. Aug 30, 2009

### ThetaPi

They are electrons. In metals, they are evenly and randomly distributed throughout the sphere since they are free to move? Delocalized electrons? I don't know. Please guide me on this.