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Electricity Unit 8, Chapter 20 Pre-unit Quiz Do the following sets of subatomic particles repel, attract, or do nothing? protonneutron proton Do nothing.

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Presentation on theme: "Electricity Unit 8, Chapter 20 Pre-unit Quiz Do the following sets of subatomic particles repel, attract, or do nothing? protonneutron proton Do nothing."— Presentation transcript:

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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.

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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

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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?

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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! R total R 1 R 2 R 3 =+++ …+ …

28 1 1 1 R total 2 3 = R total =+= 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


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