Lect01 handout

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  • Go over Daily Planner, Course Description, Lectures
  • Lectures M,W HW due 8 AM Tuesday the following week Disc Tues-Fri, the week following the lecture Quiz: due two days after Disc
  • Key to doing well is keeping up with the volume of work. Stuff comes very fast in this course. Lots of new concepts. You need to work hard and often to keep up.
  • There’s a rumor that physics 102 is harder than physics 101…..
  • Start by asking if electric force is so large, why don’t we ever feel it? Copper and wood both made of atoms, both have positive and negative charges, but are electrically very different. Why?
  • Copper and wood both made of atoms, both have positive and negative charges, but are electrically very different. Why?
  • Do the demo first, then show the visualization. Comment on how electroscope works. It’s like VandeGraaff and hair standing on end.
  • Do the demo first, then show the visualization. Comment on how electroscope works. It’s like VandeGraaff and hair standing on end.
  • Magnitude – take absolute value sign for charges, only positive sign
  • Calculate force on electron due to proton
  • Dipole of water is permanent
  • This is why water is attracted to ions & why it aligns with respect to ions (depending on charge).
  • Explains why non-polar molecules will also be attracted to ions via induced dipole
  • The do VdG demo 1121
  • Lect01 handout

    1. 1. Welcome to Physics 102! <ul><li>Electricity + Magnetism </li></ul><ul><li>(at the heart of most processes around us: </li></ul><ul><li>… in atoms & molecules; living cells) </li></ul><ul><li>Optics </li></ul><ul><li>Atomic Physics </li></ul><ul><li>Nuclear Physics </li></ul><ul><li>Relativity </li></ul>Physics 102: Lecture 1, Slide Please turn cell phones off http://www.communicationcurrents.com
    2. 2. Meet the Lecturer <ul><li>________ @illinois.edu </li></ul><ul><li>Research: </li></ul><ul><ul><li>_____________________________________ </li></ul></ul><ul><ul><li>_____________________________________ </li></ul></ul><ul><li>Office Hours: ______________________ </li></ul>Physics 102: Lecture 1, Slide
    3. 3. Course Website <ul><li>http://online.physics.uiuc.edu/courses/phys102/spring11/ </li></ul><ul><li>Daily Planner </li></ul><ul><ul><li>what you should be doing and when you should be doing it </li></ul></ul><ul><li>Course Description </li></ul><ul><li>Required Materials </li></ul><ul><ul><li>Be sure to register your I-Clicker prior to lecture </li></ul></ul><ul><li>Lectures </li></ul><ul><ul><li>posted after the lecture is given </li></ul></ul><ul><li>First Discussion: _________ </li></ul><ul><li>First Lab: _________ </li></ul><ul><li>Exam dates: _________ </li></ul>Physics 102: Lecture 1, Slide
    4. 4. Course Philosophy <ul><li>Read about it (textbook and prelecture) </li></ul><ul><li>Untangle it (lectures) </li></ul><ul><li>Play with it (labs) </li></ul><ul><li>Challenge yourself (homework) </li></ul><ul><li>Close the loop (discussion/quiz) </li></ul>Physics 102: Lecture 1, Slide The order is important!
    5. 5. Grading <ul><li>Preflights & Lectures 50 </li></ul><ul><li>Homework 100 </li></ul><ul><li>Lab (Prelab due at start of lab) 150 </li></ul><ul><li>Discussion 150 </li></ul><ul><ul><li>Take-home quizzes; drop lowest 1 </li></ul></ul><ul><li>Hour Exams (3 x 100) 300 </li></ul><ul><li>Final Exam 250 </li></ul><ul><li>1000 </li></ul>Physics 102: Lecture 1, Slide
    6. 6. Prelectures & ACTS <ul><li>Do it! </li></ul><ul><li>Answer preflights 50/1000 points </li></ul><ul><ul><li>1 point for honest attempt at preflight. </li></ul></ul><ul><ul><li>1 point for using clicker in lecture (ACTS) </li></ul></ul><ul><ul><ul><li>2 points/lecture x 25 lectures = 50 points </li></ul></ul></ul><ul><ul><ul><li>Note that there are 28 lectures, so you have some free ones </li></ul></ul></ul><ul><li>Register I-Clicker before lecture </li></ul>Physics 102: Lecture 1, Slide
    7. 7. Physics 101 <ul><li>Kinematics </li></ul><ul><li>Forces </li></ul><ul><li>Energy </li></ul><ul><li>Fluids </li></ul><ul><li>Waves (Sound) </li></ul>Physics 102: Lecture 1, Slide <ul><li>Electricity+Magnetism </li></ul><ul><li>Circuits </li></ul><ul><li>Optics </li></ul><ul><li>Modern </li></ul><ul><ul><li>Atomic </li></ul></ul><ul><ul><li>Nuclear </li></ul></ul><ul><ul><li>Relativity </li></ul></ul>Physics 102 Content Macroscopic Microscopic Prerequisite!
    8. 8. Physics 102: Lecture 1, Slide Electric charge & Coulomb’s Law Physics 102: Lecture 01
    9. 9. Origin of Charge <ul><li>Charge is an intrinsic property of matter </li></ul><ul><li>Two types: </li></ul><ul><ul><li>Positive Charge: e.g. protons </li></ul></ul><ul><ul><li>Negative Charge: e.g. electrons </li></ul></ul><ul><ul><li>Opposite charges attract. Like charges repel. </li></ul></ul><ul><ul><li>The electric force is what holds stuff together </li></ul></ul><ul><li>Atoms are neutral </li></ul><ul><ul><li>Negatively charged electrons “orbit” around positively charged central nucleus </li></ul></ul>Physics 102: Lecture 1, Slide
    10. 10. Conductors and Insulators Physics 102: Lecture 1, Slide Most things are in between perfect conductor / insulator Q: How do electrons behave in a perfect conductor? Q: How do electrons behave in a perfect insulator?
    11. 11. Electroscope (+demo) <ul><li>Conduction </li></ul><ul><ul><li>Charged rod is brought near scope </li></ul></ul><ul><ul><li>Charged rod touches scope transferring some charge </li></ul></ul><ul><ul><li>Scope is left w/ same charge as rod </li></ul></ul>Physics 102: Lecture 1, Slide + + + + + + + + + + + + + + + + + + + + charge + + + + + + + + + + + + + + + + + + + + charge + + + + + + + – + + + + – – – – + + + + + + +
    12. 12. Electroscope (+demo) <ul><li>Induction </li></ul><ul><ul><li>Charged rod is brought near scope </li></ul></ul><ul><ul><li>Scope is briefly grounded allowing charge to flow on (or off) scope </li></ul></ul><ul><ul><li>Scope is left w/ opposite charge as rod </li></ul></ul>Physics 102: Lecture 1, Slide - - - - - - - - - - – – – – – – – – – - charge – + + + + – – – – + + + + + + + – + + – – – – + + + + + + + + + + +
    13. 13. ACTS <ul><li>A negatively charged rod is used to charge an electroscope by induction . What is the resulting net charge on the electroscope? </li></ul>Physics 102: Lecture 1, Slide A) positive B) zero C) negative <ul><li>If the conducting electroscope were replaced by an insulating ball and then charged by induction as above, what would be the net charge on the ball. </li></ul>A) positive B) zero C) negative
    14. 14. Coulomb’s Law <ul><li>Force between charges q 1 and q 2 separated a distance r: </li></ul>Physics 102: Lecture 1, Slide Magnitude Or: “ Coulomb constant” “ Permittivity of free space” Direction Opposite charges attract, like charges repel
    15. 15. Coulomb’s Law <ul><ul><li>F = k q 1 q 2 /r 2 k = 9x10 9 Nm 2 /C 2 </li></ul></ul>Physics 102: Lecture 1, Slide Example Magnitude <ul><li>What is the magnitude of the force on the proton due to the electron in hydrogen? </li></ul>+ - r = 1x10 -10 m Q p =1.6x10 -19 C Q e = -1.6x10 -19 C
    16. 16. ACT: Coulomb’s Law <ul><li>What is the direction of the force on the proton due to the electron? </li></ul><ul><ul><li>(A) Left (B) Right (C) Zero </li></ul></ul><ul><li>What is the direction of the force on the electron due to the proton ? </li></ul>Physics 102: Lecture 1, Slide + - r = 1x10 -10 m q p =1.6x10 -19 C q e = -1.6x10 -19 C
    17. 17. Physics 102: Lecture 1, Slide Electric dipole A positive and negative charge of equal magnitude separated by a (usually small) distance + – – Q +Q Ex: water = = H O  +  +  - H
    18. 18. ACT Physics 102: Lecture 1, Slide + - – An electric dipole is placed near a large negative charge. What is the net force on the two connected charges? A) Left B) Zero C) Right
    19. 19. ACT: Induced Dipole <ul><li>1) Nothing </li></ul><ul><li>2) Attracted to charged sphere. </li></ul><ul><li>3) Repelled from charged sphere. </li></ul>Physics 102: Lecture 1, Slide – <ul><li>An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? </li></ul>
    20. 20. Induced Dipole Physics 102: Lecture 1, Slide <ul><li>An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? </li></ul>– + + + + – – – –
    21. 21. Demo: Induced Dipole Physics 102: Lecture 1, Slide <ul><li>An uncharged conducting sphere is hung between a charged sphere and a grounded sphere and held midway between the two. What happens when the uncharged sphere is released? </li></ul>–
    22. 22. Summary of Today’s Lecture <ul><li>The concept of charge </li></ul><ul><li>Conductors and insulators </li></ul><ul><li>Coulomb’s Law for the force between charges </li></ul><ul><ul><li>Much more on Coulomb’s Law in next lecture </li></ul></ul><ul><li>Electric dipoles (permanent & induced) </li></ul>Physics 102: Lecture 1, Slide

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