Chapter 9.5 & 9.6Chapter 9.5 & 9.6

Charging by Contact & Insulators and Conductors

Charging by ContactCharging 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.

Charging by ContactCharging by ContactThink 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?

Insulators and ConductorsInsulators 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.

Insulators and ConductorsInsulators 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.

Common Insulators and Common Insulators and ConductorsConductors

Good Fair GoodConductors Conductor Insulator

Copper Carbon FurGold Human body

RubberMercury Earth WoodIron Water Vapour Paper

QuestionsQuestions

• P.279 #2 & 3• P.281 # 2,4 & 6