1. Charging by Contact & Insulators and Conductors
Chapter 9.5 & 9.6
Charging by Contact & Insulators and Conductors

2. Charging by Contact
Charging by contact occurs as the result of one object already being charged.
For example, after you have crossed a carpeted floor, your body may be negatively charged. The door knob is usually uncharged.
Your body then shares the electric charge with the doorknob through “contact”.
Actually, your hand does not even get to touch the doorknob before the charge begins to transfer in the form of a spark.

3. Charging by Contact Think about it!!!
Why would we have to wear special shoes and clothes in:
A coal mine?
A hospital operating theatre?
Parts of an oil refinery?

4. Insulators and Conductors
In order to use electricity to our advantage, we need both insulators and conductors.
An insulator is a substance which slows the free movement of electrons from atom to atom.
A conductor is a substance in which electrons can move freely from one atom to another.

5. Insulators and Conductors
Since insulators do not allow the free movement of electrons, they can encourage the build up of static charge on the surface.
On the other hand, since conductors such as copper allow the free movement of electrons, a static charge can never build up.

6. Common Insulators and Conductors
Good Fair Good
Conductors Conductor Insulator
Copper Carbon Fur
Gold Human body Rubber
Mercury Earth Wood
Iron Water Vapour Paper

7. Questions
P.279 #2 & 3
P.281 # 2,4 & 6