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Electricity Unit 8, Chapter 20

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Pre-unit Quiz Do the following sets of subatomic particles repel, attract, or do nothing? protonneutron proton Do nothing Repel Page 1

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electronneutronelectronprotonelectron Do nothing Repel Attract Page 2

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I. Electric Charges 1. Positive (+) 2. Negative (-) A. Types of electric charges B. Properties of electric charges 1. Like charges repel 2. Opposites attract ++ +- (Force of repulsion) (Force of attraction)

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C. An object gains an electric charge by gaining or losing electrons + - + + + + + + + + + - - - - - - - - - Two neutral objects Positive objectNegative object

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II. Static electricity A. Build up of electric charges B. There are three ways to separate electric charge.

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The first method of separating electric charge: FRICTION before after Electrons transfer when two objects are rubbed against each other.

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The second method of separating electric charge: Induction before after A neutral object is charged oppositely when brought near a charged object.

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The third method of separating electric charge: Conduction before after contact allowed Electrons are transferred through contact.

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Learn more C. Van de Graaff generator friction static electric field electroscope - detects electric fields static electric discharge ground wire Robert Van de Graaff

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D. Thunder storms ice crystals + updraft friction induction static discharge static discharge

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III. The flow of electricity A. Voltage (V) 1. Pushes the electrons through a wire (analogous to water pressure in a pipe) 2. Called potential difference 3. Measured in volts Bonus: Named after Count Alessandro Antonio Anastasio Volta Count Volta invented the battery.

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4. Sources of voltage a. Batteries (chemical reaction) b. Solar cells (light) c. generator (mechanical/magnetic) solar cell generator

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B. Current (I) 1. Flow of electrons through a wire (analogous to the flow of water in a pipe) 2. Measured in amperes or amps 3. Detected by an ammeter Bonus: Named after André Marie Ampère Made discoveries in electromagnetism concerning electric current

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4. Two types of current a. alternating current- AC - current regularly changes direction - can be transmitted over long distances - produced by generators

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b. direct current- DC - produced by batteries and solar cells - current travels in one direction only

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C. Resistance (R) 1. Opposes the flow of electrons (analogous to a blockage in a water pipe) 2. Measured in ohms ( ) What would cause the resistance in these pictures?

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3. Factors that affect resistance of a wire a. length b. thickness

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c. temperature d. type of material - reducing temperature reduces resistance

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D. Ohm’s Law Voltage 1. Current = Resistance volts 2. amps = ohms V V I = 3. I = R R Georg Simon Ohm

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IV. Circuits A. A circuit is a complete loop for electrons to flow around B. Circuit symbols 1. wire 2. switch 3. resistor 4. light 5. battery 6. ammeter 7. voltmeter + - V A

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C. Series circuit 1. Has only one path or loop 2. Total resistance equation R total = R 1 + R 2 + R 3 + … 2 3 R tot = 2 + 2 + 3 = 7 2 + -

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D. Parallel circuit 1. Has more than one path or loop 2. Total resistance equation THIS ONE IS TRICKY! 1 1 1 1 R total R 1 R 2 R 3 =+++ …+ …

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1 1 1 R total 2 3 =+ 1 3 2 5 R total 6 6 6 =+= 6565 R total = = 1.2 2 3 + -

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My Electric Bill

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Electric companies multiply your electric use by A cost per KWH.

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V. Electric Power A. Power is measured in Watts (W) B. Power = voltage X current P = VI Watts = volts x amps James Watt invented the steam engine

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VI. Electric Energy A. Energy is measured in kilowatt-hours (kWh) B. Energy = Power X time E = Pt kWh = kilowatts x hours PP&L’s definition

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