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Daily Work Organizer Tuesday Question of the Day: Why are objects attracted to each other? Do Now: Turn to page 231 and write responses to the questions about electricity. You may discuss your ideas with your partner. Agenda: Cornell Notes Homework: Homework (2) Reading Log 24: pg 235236 Due Friday: New HW System 1. HW is stamped 2. You write the number on the top of the assignment (#1) Reading Log 23 3. Staple all your HW in order to the back of your Cornell notes at the end of the chapter Jobs 1 PowerPoint Master 2 Graded Work Gurus 1 Whiteboard Cleaner! Tuesday Tutoring Everyone is Welcome! Mandatory if your grade is below a C If you can’t make, you must provide Ms. Gamm with a written or oral explanation. It’s what we see… Static Electricity The Point of Cornell Notes If you don’t review, you would need to spend 40Without Review, only about 20% of 50 minutes re-learning each hour of material information is remembered after initial later memorization • Within 24 hours spend 10 minutes reviewing • A week later spend 5 minutes to "reactivate" the same material Write Questions! Write the Summary Charges •Rubbing plastic or glass makes them attract to bits of paper or dust •Same objects charged the same way will repel each other •Some charged objects attract each other Charges •All charged objects either attract or repel each other •This implies 2 types of charges •Benjamin Franklin decided to call the charge on rubbed glass positive Electricity •One of the first objects to hold this charge was amber •The Greek word for amber is elektron •Electricity •Electron Charge •To understand Charge, let’s look at the atom •Protons (nucleus) are positively charged •(repels charged glass) •The electrons are negatively charged •(attracts charged glass) Charge •Even though protons are much bigger (2,000 x’s bigger than electron), the – and + charges are the same size. •If an atom has equal number of electrons and protons the charge is zero. ____? •3 electrons (blue) and 3 protons (red) •Net charge is zero (neutral charge) Charge Rules •In order to be charged, an object must have extra protons or electrons •The following facts help understand charges: 1. In solids, positive charges do not move protons are fixed in place Charge Rules 2. In solids, negative charges can move • conductors: electrons move all about material Charge Rules 2. In solids, negative charges can move • conductors: electrons easily move about material • insulators: electrons mostly move around atom Charge Rules 3. In fluids, both protons and electrons can move all around Charge Rules 4. Objects want to be neutral. • If given a path to the earth, electrons will flow out until the object is neutral. • This is called grounding. v Charge by Rubbing •Every atom attracts electrons (e-) a certain amount •When you rub two objects together the object that attracts electrons more will steal e- + − Charge by Rubbing •This stealer becomes negative (more e-) and the other object becomes positive (lost e-) What will happen to the charge when the bars separate? 46Electrons Electrons 42Electrons Electrons Transferring Charge •This stealer becomes negative (more e-) and the other object becomes positive (lost e-) •Only works if there is contact Daily Work Organizer Wednesday Question of the Day: How do electrons move? Do Now: 1. Graph your Test Score on your Tracker 2. Answer and give an explanation to questions #1 & 2 on pg 244. Hint: Q and 2Q represent charge Agenda: Cornell Notes Activity Cornell Notes Homework: (3) Reading Log 25: pg 248Homework 252 (4) Finish Activity pg 238-239 (5) Problems 1-3 Pg 246 1. 2. Where is the Electrostatic Electrostatic Force greatest? smallest? Q = charge Test Corrections due Monday Retake: Monday 3:15 – 4:15 Warning If you do not return your test to me you get -10 points All tests must be returned by Tuesday Conduction ① A charged conductor touches a neutral conductor Total Charge = protons - electrons Conduction ① A charged conductor touches a neutral conductor Q1 = ? Q1 = 3 protons + 7 electrons = -4 charge Q2 = ? Q2 = 4 protons + 4 electrons = 0 charge Conduction ① A charged conductor touches a neutral conductor ② The electrons spread out so that the charges on both are equal Q1 = Q2 = -2 charge What will happen to the charge when the conductors separate? Conduction ① A charged conductor touches a neutral conductor ② The electrons spread out so that the charges on both are equal Q1 = Q2 = -2 charge Visualizing Electric Charge pg 237 Neutral Draw 3 units of charge (protons & electrons) In each bar Induction pg 237 6 units of charge (protons or electrons) 9 protons & 9 electrons total Neutral Conduction pg 238 6 units of charge (protons or electrons) What happen Total can protons: 6+9 = 15 when charged= 9 Total2electrons objects touch? Difference: 6 protons Charge has to be evenly 9 protons totalelectrons distributed… How many should each object have? Initially Neutral Charging by induction pg 239 6 units of charge (protons or electrons) Charged objects want to be neutral… 9 protons & How many electrons 9 electrons totalshould enter from the ground? Neutral Vocab Charging by Induction Word Picture that reminds you of definition A method used to charge an object without actually touching the object to any other charged object Definition Sentence using word Word or words that remind you of definition Vocab Charging by conduction Word Picture that reminds you of definition Electrons are transferred from one material to another through contact Definition Sentence using word Word or words that remind you of definition Induced Polarity •How do charged objects attract neutral objects? •By inducing a charge on the neutral object. •A neutral balloon has no effect on wall’s e•The neutral wall has efound randomly around nuclei of the atom Induced Polarity •Let’s charge the balloon •Now the e- in the wall are being repelled •This leaves the exposed wall acting positive •Negative and positive charges attract each other What was wrong with this movie? Electrostatic Force •Electric Force is 1039 times larger than gravity •Coulomb studied charge with charged metal balls •Let’s look at how the amount of charge on each ball and the distance effect the electrostatic force Coulomb’s Law •Electrical force is proportional ( FE µ Q1Q2 1 FE µ 2 d µ) to both Coulomb’s Law •These lead to one equation called Coulomb’s Law: kQ1Q2 FE = 2 d FE ºElectric Force in Newtons (N) Q1,Q2 ºcharge in Coulombs (C) d º distance between centers in meters (m) k º 9.0 ´10 9 N× m 2 C2 Coulomb’s Law •A Newton is about equal to ¼ pound •A Coulomb is the amount of charge in 6.25 x 1018 electrons or protons kQ1Q2 FE = 2 d Example Two charged spheres, one with 1x1012 extra electrons and one with 2x1012 extra protons are separated by 50 cm. What force do they exert on each other? Given: d = 50cm ( 1m 100 cm Q1 = -1´10 ( ( )= 0.50 m ) = -1.6 ´10 C ) = 3.2 ´10 C -7 12 1Coulomb Q2 = 2 ´10 12 Want: FE 18 6.25´10 1Coulomb 6.25´1018 -7 Example solve for FE kQ1Q2 FE = 2 d FE = (9 ´10 9 N ×m 2 C2 -7 -7 )(-1.67 ´10 C)(3.2 ´10 C) (0.50 m) 2 FE = - 0.0019 N - force is attractive Time to practice Go to pg. 235 Daily Work Organizer Friday Question of the Day: What is an electric filed? Do Now: Answer questions 3, 4, 11 & 12 on pg 244 Agenda: Labette Cornell Notes Activity Homework: (7) Reading Log 26: 255-256 Homework (8) Problems Set 8 (9) Finish E-field activity 253 Test Corrections! Daily Work Organizer Friday Question of the Day: What is an electric filed? Do Now: Answer questions 3, 4, 9, 11 & 12 on pg 244, Agenda: Labette Cornell Notes Activity Homework: (7) Reading Log 26: 255-256 Homework (8) Problems Set 8 Test Corrections! Answers 1. 2. 3. 4. 5. 6. 7. A C A C E A B 8. A 9. D 10. B 11. A 12. A 13. B If distance is doubled: dfinal = 2dInital FE initial = 12 N 1 FE µ 2 d 1 FE µ (2d)2 1 FE µ 2 4d #3 1 1 FE µ 2 4d 12 FE final µ N 4 Tutoring After School Today, room 308 Static Electricity Test on Tuesday Why? Because I don’t want you that have to study over Thanksgiving Advice: Finish your Cornell notes over the weekend Labbette pg 240 Read pg 240 Complete Part 1 with your lab group The Electric Field •All charged objects produce electric fields •We know that a positive charge will repel another positive charge and attract a negative one •If we draw lines to represent this we would be drawing an electric field The Electric Field Let’s look at the rules for drawing field lines: ① Field lines always point in the direction that a positive test charge would move The Electric Field ② Field lines always intersect charged objects at right angles The Electric Field ② Field lines always intersect charged objects at right angles The Electric Field ③ Field lines never intersect each other The Electric Field ④ The closer that field lines are to each other, the greater the electric field The Electric Field Example: •Draw the electric Field Lines Time to practice Go to pg. 253 Electric Field in Conductors •Imagine a charged circle •Where can charges move to get farthest away? Electric Field in Conductors •Imagine a charged circle •Where can charges move to get farthest away? •To the edges! •The excess charge on a conductor will always be on the surface Electric Field in Conductors •How would the field effect a lone charge in the middle? Electric Potential •Which is worse, 120 volts or 25,000 volts? •depends •Voltage is a potential for energy per charge E and E = Vq V= q 1 volt = 1 Joule of energy per 1 Coulomb of charge 1 Joule 1 volt = Coulomb Electric Potential •What makes voltage dangerous is how fast the charge flows out •1 Joule is about the energy required to lift half a glass of water 1 meter high 1 J! 1m Electric Potential •Basic outlet is 120 V •The flow of an outlet is about 20 Coulombs/sec •The energy released in 1 sec would be: E = Vq E = (120V)(20C) = 2,400 J Amount of energy to lift 75 gal of water 1 m high! Electric Potential •Van de Graff generator carries up to 400,000 V! •But, it only flows 10 μCoulombs/sec •The energy released in 1 sec would be: E = Vq 5 J -6 E = (4 ´10 C )(10 ´10 C) = 4 J Amount of energy to lift 2 cups of water 1 m high Time to practice Go to pg. 253