Electricity and Electrical Charges What is electricity? All the phenomena caused by positive and negative charges. Where do these charges come from?

Definitions Static Charge – is a build up of electricity that is waiting to be expelled. Thus, the person/object that is charged is at rest. Hence, a static charge. Discharge – occurs once you bring a charged object near another non charged object, the amount of electricity is released. Electrostatic – is the study of static electric charges

Electrons: Nucleus: Located outside nucleus Contains protons (+) & neutrons (no charge) Overall positive charge (+) Contains nearly all mass (dense) Electrons: Located outside nucleus Easily moved, lost or gained Negative charge (-)

Electrical Charges: - All matter has electrical charges There are two types of charges: Positive Negative + -

Negatively charged objects: contain more electrons (-) than protons (+). Positively charged objects: contain fewer electrons (-) than protons (+). Only negatively charged electrons can move from one object to another and if you have an equal number of protons and electrons, the object is neutral.

Law of Charges Attraction Repulsion Opposite charges Law of Electrical Charge – like charges repel and unlike charges attract. There are 2 forces between charged objects: Attraction Repulsion Opposite charges “Opposites Attract” Same charges “Like repel” Law of Charges

- + Ex #1 A B A POSITIVE Opposites Attract! Sphere A is negatively charged. When placed beside sphere B, they attract. What is the charge on B? POSITIVE Opposites Attract! A B A - +

- + + + - + Ex #2 Attract A C A B B C Three charged spheres are suspended next to each other. If sphere A is negatively charged, what will happen when sphere A & C are suspended beside each other? Attract A C A B B C - + + + - +

+ + + - - + Ex #3 A B B C C D Repel Four charged spheres are suspended next to each other. What will happen if A & D were suspended next to each other? Repel A B B C C D + + + - - +

What would happen if “B” & “C” were brought together? You have three charged objects – A, B & C in a lab. You record the following results: Ex #4 Test Observation Bring “A” near “B” They repel Bring “A” near “C” They attract + + + - + - What would happen if “B” & “C” were brought together? They would attract!!!

Assignment Page 278 1, 2, 4, 5, 7, 9, 12, 13 (a)