1. The Particle Model of Electricity and Atomic Structure
Nature of Electricity: Part 2

2. Review
What is the model that we now accept for explaining how charges work?
What charges attract each other?
What charges repel each other?

3. Particle Model of Electricity
Introduction:
Where have you heard the word ‘Particle’ before?
How do you think that applies to the Particle Model of Electricity?

4. Atomic Model Materials that posses charge are made up of ATOMS.
The charge of an atom depends on the number of electrons
(NEGATIVE) or
protons (POSTIVE).

5. Atomic Model
The nucleus cannot move from the atom, therefore the protons (POSTIVE) cannot move from the atom.
The nucleus has an overall POSTIVE charge
The electrons (NEGATIVE) can move from the atom.

6. Particle Theory of Electricity
1. Two types of subatomic particle are important in the theory: electrons (-ve) and protons (+ve)
2. Charge cannot be created or destroyed- charge is CONSERVED

7. Particle Theory of Electricity
3. Positive charges are fixed and negative charges are free to move.
4. A neutral object has equal numbers of positive and negative charge.

8. Part 3 of Particle Theory of Electricity: Negatives can move

9. Part 4 of Particle Theory of Electricity: Neutral Object
EQUAL AMOUNTS OF BOTH POSTIVE AND NEGATIVE CHARGES MAKES THIS OBJECT NEUTRAL

10. Particle Theory of Electricity
5. A negative object has an excess of negative charge. A positive object has a deficit of negative charge.
6. Charge is shared by contact. Materials which allow charge to move easily are called conductors, and materials that do no allow charge to move easily are called insulators.
7. Like charges repel; unlike charges attract.

11. Attraction of Neutral Objects to Charged Objects
Neutral objects have a balance of both positive and negative charges.
If they have that balance, why would they be attracted to charged objects?
The difference lies in the difference between INSULATORS and CONDUCTORS

12. Attraction of a Neutral Object (Insulator)
Materials like paper, which do not allow the free movement of electrons, are called insulators.
The charges on insulators do not separate readily but polarize (align themselves). Since opposite charges are always closer to each other, there is a net force of attraction.

13. Explanation
If you bring a POSTIVELY charged ruler near bits of paper (INSULATOR), the paper will be attracted to the ruler.
If you bring a NEGATIVELY charged ruler near bits of paper (INSULATOR), the paper will be attracted to the ruler.
This is because the charges in the paper are aligning opposite to what ever charge the ruler has.
The charges stay together, but align depending on what charge they are attracted to.

15. Attraction of a Neutral Object (Conductor)
Metals, allow the free movement of negatives, and are called conductors.
The charges on conductors separate readily, and are some distance apart from each other.

16. EXPLANATION
The pith ball (CONDUCTOR) is neutral and if you bring a charged rod to it the pith ball will be attracted to it.
The negatives (electrons) are free to move, so they move towards the positive charge of the rod.
If the pith ball and rod touch, the negatives on the pith ball are attracted to the rod making the rod less positive and the pith ball more negative.