ELECTROSTATICS Electric Force

Whiteboard Particle Model (remember sticky tape lab?) How you can make a balloon stick on the wall? What is occurring on the atomic level that lets you do this?

The atom The positive charge cannot move The atom has positive charge in the nucleus, located in the protons. The positive charge cannot move from the atom unless there is a nuclear reaction. Electrons can move The atom has negative charge in the electron cloud on the outside of the atom. Electrons can move from atom to atom without all that much difficulty. You charge the balloon by rubbing it on hair or on a sweater, and the balloon becomes negative. How can it stick on a neutral wall?

Whiteboard Particle Model (remember sticky tape lab?) 1. How you can make a balloon stick on the wall? 1. What is occurring on the atomic level that lets you do this? Wall

Molecules in the wall become polarized. Electrons move away from the surface repelled by the excess negative charge on the balloon. This creates a positive surface that the balloon can stick to + - Wall

What is making them repel? A force

Whiteboard Particle Model What happens to the vanes of the electroscope when you bring a negatively charged object near it? What is occurring on the atomic level that makes the vanes do this? Pole Vanes

Electrons are repelled by the negative charge and are conducted into the vanes. The vanes become negative and repulsive.

What is making them repel? A force

If Object is Positive (no whiteboard) What happens to the vanes? Pole Vanes

If Object is Positive (no whiteboard)

What is making them repel? A force

Coulomb’s Law Coulomb’s law tells us how the magnitude of the force between two particles varies with their charge and with the distance between them. k = 8.99  10 9 N m 2 / C 2 q 1, q 2 are charges (C) r is distance between the charges (m) F is force (N)

What direction are the forces on C? +-- AB C Net Force is in what direction? To the left