# 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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Electricity Unit 8, Chapter 20

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

electronneutronelectronprotonelectron Do nothing Repel Attract Page 2

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)

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

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

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

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

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

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

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

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.

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

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

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

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

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?

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

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

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

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

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  + -

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 =+++ …+ …

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

My Electric Bill

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

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

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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