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ELECTRICITY----STATIC AND CURRENT What is happening in these pictures? STATIC ELECTRICITY A BUILD UP OF CHARGE( electrons ) from one object to another, without a flow of charge. 3 ways to create static electricity: 1.conduction: build up of charge by direct contact between 2 objects Van de graph machine 2. Induction: build up of charge by force of attraction or repulsion WITHOUT touching one object to the other ( through open space ) Balloon Demo with Salt ( sugar ): An electroscope demonstrates induction Static electricity by friction 3. Friction: build up of charge by rubbing one object against another. Rubbing hair with balloon Static friction- study jams • http://studyjams.scholastic.com/studyjams/ja ms/science/energy-lightsound/electricity.htmhttp://studyjams.scholas tic.com/studyjams/jams/science/energy-lightsound/electricity.htm Write the letter that most applies for each word. 1.___ Repel 2.___ Electroscope 3.___ Attract A. Objects with opposite charges come together. B. Detects charges. C. Objects with like charges jump apart. Answer the questions. State the Law of Electric Charges: _______________________________________ ____________________________________ List the three ways in which an object can become charged: 5) 6) 7) When an object becomes charged, one object ________ electrons, and one object _______ electrons. multiple choice: _____ Electric force is found between a) Charged objects b) credit cards c) criminals _____ The area around a charged particle that can exert a force is called : a) electric force b) electric shock c) electric field 11. ______ The build up of electric charges on an object is a) current electricity discharge b) static electricity c ) electric Use the word bank to select your BEST answer. FRICTION (f) INDUCTION (i) CONDUCTION (c) 12._____Electrons transferred from one object to another by direct contact. 13.____ Charges on an object rearrange without direct contact when a charged object is near it. 14. ____Rub 2 objects together. The electrons are transferred. 15. ____Rub a balloon on a wool sweater, and place it near a wall. 16. ____ Walking across a carpet. E. True /False. CORRECT the False!! 17.____ A lightning bolt is an example of electric discharge. 18.____ An electroscope can tell if the charge is pos. or neg. 19.____ Static electricity is NOT as noticeable in the summer because of the dryness in the air. 20._____ Lightning is a result of the negative charges in the clouds being attracted to the negative charges on the ground. http://phet.colorado.edu/en/simulation/ballo ons2011 electricity.ppt Lightning video • http://player.discoveryeducation.com/index.cf m?guidAssetId=5AE05296-1087-4C59-A5B94585869125DC&blnFromSearch=1&productco de=US Ice hockey simulation • http://phet.colorado.edu/en/simulation/elect richockeyhttp://phet.colorado.edu/en/simulatio n/electric-hockey Current electricity • Current is a flow of electric charges. It is not a build up of charge that is discharged. • All current elec. needs a circuit—a pathway for electric charges to flow.. • All circuits must have at least 3 parts : 1) wires, 2) a source and 3) a load(s). Parts of a circuit wires Load Source of electricity Conductors • Conductor: a material that easily allows the flow of electric charges. • It gives very little resistance to the flow of charge. ( metals – copper, aluminum , etc ) Insulators • Insulators: do not easily allow for the flow of electric charges through them. • Ex: glass, plastic, certain rubber materials, cloth. Current electricity– brain pop http://www.brainpop.com/technology/e nergytechnology/currentelectricity/ • http://www.brainpop.com/technology/energy technology/currentelectricity/ Types of circuits • http://www.brainpop.com/science/energy/ele ctriccircuits/http://www.brainpop.com/scienc e/energy/electriccircuits/ Law of electric Charges • Like Charges repel; Unlike charges attract. 2 main types of circuits • 1. Series Circuit: only 1 path for the electric charges to flow • 2. Parallel Circuit: has More than one path for the electric charges to flow. Series circuit Now, let’s draw it in your notes: Resistance • This is what “slows down” the movement of the electric charges … so they hit each other more… • What do you think could ADD resistance in a circuit ? • Add more loads to the same circuit • Heat • Longer wires • Thinner wires Circuit Mini Lab • Take a sheet of computer paper. • You have 4 drawings, 4 circuits to build, and 4 questions to answer… Let’s do the drawings together, then you can build, and answer the questions: • You Label: wires, source, load, direction, terminals, switch • 1. 3. • 2. 4. 2. Parallel Circuit: has more than 1 path for electric charges to flow, so if 1 load goes “out,” the other loads will still work ! Draw a parallel circuit Circuit simulation http://phet.colorado.edu/en/simulation/circu it-construction-kit-dc Alternating Current - AC • Electric charges move back and forth—homes and buildings. Ex: 60 V one way and 60 V the other way,= 120 Volts Let’s recap: • 2 types circuits 2 types current direction Series Direct current 1 way Parallel Alternating current Back and forth Direct with a battery One way BATTERIES CONVERT CHEM. ENERGY TO ELECTRICITY. 2 TYPES: A)DRY CELLS B)WET CELLS Dry cells have pastelike electrolytes, and these are the batteries you are used to using. Wet cells have liquid electrolytes. ( car batteries) • Electrolytes- liquids/acids that cause a chem. reaction, that releases electric charges • Batteries (usually) are DCdirect current- where the electrons flow only in 1 direction. dry cell Wet cell Inside a dry cell Inside a wet cell Watch the stick figures move the charges Back and forth, creating a potential difference In voltage, making current ! http://phet.colorado.edu/en/simulation/batte ryvoltagehttp://phet.colorado.edu/en/simulati on/battery-voltage Circuit breakers and fuses Circuit breaker-open a circuit to keep from Overload. Plug fuses • Circuit breaker fuses CURRENT RESISTANCE VOLTAGE V SYMBOL: I UNITS: Amperes R or OHM’S WHAT IS IT? The # of electrons. the rate at which charges pass a given point The opposition to the flow of electrons; High resistance has more opposition to the flow The energy of each electron. Temperature Length Wire Type of wireCopper-good conductor; decrease R; Iron- poor conductor; increase R energy Volts Low voltage = little energy. 4 THINGS THAT AFFECT R: High Voltage = High Thin/thick wires More electrons=more ↓ Thickness = ↑ R current; ↑ Temperature =↑ R less electrons = less ↑ Length = ↑ R current Ohm’s law I = V/ R Current = voltage/ resistance. •Discuss wires and resistance!! •What current would flow through a resistor of 20 ohms connected to a 12 V supply? • [A] 240 A • [B] 1.66 A • [C] 0.67 A • [D] 0.067A What current would flow through a resistor of 40 ohms connected to a 10 V supply? • [A] 400 A • [B] 4 A • [C] 0.25 A • [D] 0.025A A 100 ohm resistor is connected to a 20 V supply. What current flows? • [A] 0.02 A • [B] 0.05 A • [C] 0.2 A • [D] 0.5 A • [E] 2000 A What value of resistor would be used to permit a current of 0.2 A to flow using a 6V supply? • [A] 0.03 ohms • [B] 0.3 ohms • [C] 3.0 ohms • [D] 30 ohms • [E] 300 ohms