2. Electricity Unit 8, Chapter 20

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

4. electronneutronelectronprotonelectron Do nothing Repel Attract Page 2

5. 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)

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

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

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

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

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

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

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

13. 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.

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

16. 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

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

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

20. 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?

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

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

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

25. 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

26. 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  + -

27. 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 =+++ …+ …

28. 1 1 1 R total 2 3 =+ 1 3 2 5 R total 6 6 6 =+= 6565 R total = = 1.2  2  3  + -

29. My Electric Bill

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

31. 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

32. 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