1. The Theory of Electricity
All substances are made of protons (positive) and electrons (negative).
Undisturbed objects have a neutral charge, since the number of protons and electrons is equal.
What is the charge on this object?

2. Some objects, when rubbed, pick up electrons from the material that is doing the rubbing.
As a result the rubbed object becomes negatively charged and the material becomes positively charged.

3. This table lists materials in order of their electron affinity
The tendency of a substance to hold on to electrons is called electron affinity
Tend to lose electrons
Tend to gain electrons
(+)
Human skin (dry)
Glass
Human hair
Nylon
Cat fur
Silk
Cotton
Steel
Wood
Amber
Ebonite
Plastic wrap
Teflon
(-)
This table lists materials in order of their electron affinity

4. The 3 Laws of Electrical Charges
1) Opposite charges attract each other.
2) Like charges repel each other.
3) Charged objects attract neutral objects.

5. How do objects become charged?
1. Friction: when object rub against each other

6. 2. Contact: when electrons transfer from the charged object to the neutral object that it touches

7. 3. Induction: the movement of electrons within an object caused by a nearby charged object, without direct contact

8. Making Use of Static Electricity
1. Spray Painting
The paint coming out of the nozzle gains a negative charge through friction…
The car is grounded (neutral) – therefore the paint is attracted to the car! Less waste and a smooth finish.
Car is grounded because of rubber tires or a ground strap (piece of rubber hanging from the car).

9. 2. Electrostatic Precipitators
Particulate matter (PM) passes through a mesh that charges it negatively.
Then the PM is attracted to positively charged collecting plates along the smoke stack.
Used in industrial plants such as cement, steel and lumber.