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Welcome to Physics 102!. Electricity + Magnetism Optics Atomic Physics Nuclear Physics Relativity. Please turn cell phones off. Meet the Lecturer. Alan Nathan a-nathan@uiuc.edu Research Experimental Nuclear/Particle Physics Physics of Baseball
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Welcome to Physics 102! • Electricity + Magnetism • Optics • Atomic Physics • Nuclear Physics • Relativity Please turn cell phones off Physics 102: Lecture 1, Slide 1
Meet the Lecturer • Alan Nathan a-nathan@uiuc.edu • Research • Experimental Nuclear/Particle Physics • Physics of Baseball • see http://webusers.npl.uiuc.edu/~a-nathan/pob • Office Hours: Monday 11-12 • or drop in any time and I’ll talk with you if I am not otherwise tied up 04 Physics 102: Lecture 1, Slide 2
Course Format • http://online.physics.uiuc.edu/courses/phys102/spring08/ • Daily Planner • what you should be doing and when you should be doing it • Course Description • Lectures • posted just after the lecture is given Physics 102: Lecture 1, Slide 3
Course Philosophy • Read about it (textbook and prelecture) • Untangle it (lectures) • Play with it (labs) • Challenge yourself (homework) • Close the loop (discussion/quiz) the order is important! Physics 102: Lecture 1, Slide 4
Course Format(Spiral Learning) • Preflights 50 • Homework 100 • Lab (Prelab due at start of lab) 150 • Discussion 150 • Take-home quizzes; drop lowest 1 • Hour Exams (3 x 100) 300 • Final Exam 250 1000 07 Physics 102: Lecture 1, Slide 5
950-1000 A+ 920-949 A 900-919 A- 880-899 B+ 860-879 B 835-859 B- 810-834 C+ 780-809 C 750-779 C- 720-749 D+ 690-719 D 610-689 D- <610 F Grading Scale Physics 102: Lecture 1, Slide 6
Prelectures & Lecture • Do it! • Answer preflights 50/1000 points • 1 point for honest attempt at preflight. • 1 point for using clicker in lecture (75%) • 2 points/lecture x 25 lectures = 50 points 10 Physics 102: Lecture 1, Slide 7
P102 Lectures • Not everything you need! • Lectures: Concepts, Connections, Motivation • Textbook: Comprehensive • Homework + Discussion: Calculations • Lab: Hands-On • Taking Notes • Lecture notes are available at bookstore or online • Some key pieces for you to fill in 15 Physics 102: Lecture 1, Slide 8
Content Physics 101 Physics 102 • Kinematics • Forces • Energy • Fluids • Waves (Sound) Macroscopic Microscopic • Electricity+Magnetism • Circuits • Optics • Modern • Atomic • Nuclear • Relativity 18 Physics 102: Lecture 1, Slide 9
Origin of Charge • Charge is an intrinsic property of matter • Two types: • Positive Charge: Protons • Negative Charge: electrons • Opposite charges attract. Like charges repel. • Atoms are neutral • Negatively charged electrons “orbit” r~10-10 m • Positively charged central nucleus r~10-15 m 20 Physics 102: Lecture 1, Slide 10
Q: How do electrons behave in a perfect conductor? Q: How do electrons behave in a perfect insulator? Conductors and Insulators Most things are in between perfect conductor / insulator 23 Physics 102: Lecture 1, Slide 11
Electroscope • Conduction • Charged rod is brought near scope • Charged rod touches scope transferring some charge • Scope is left w/ same charge as rod • gold leaves repelfly apart 27 Physics 102: Lecture 1, Slide 12
Electroscope • Induction • Charged rod is brought near scope • Scope is briefly grounded allowing charge to flow on (or off) scope • Scope is left w/ opposite charge as rod 27 Physics 102: Lecture 1, Slide 13
ACTS • A negatively charged rod is used to charge an electroscope by induction. What is the resulting net charge on the electroscope? A) positive B) zero C) negative • 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. A) positive B) zero C) negative 32 Physics 102: Lecture 1, Slide 14
Qp=1.6x10-19 C Qe = -1.6x10-19 C + - r = 1x10-10 m Example Coulomb’s Law • Magnitude of the force between charges q1 and q2 separated a distance r: F = k q1q2/r2k = 9x109 Nm2/C2 • Force on electron in Hydrogen atom 34 Physics 102: Lecture 1, Slide 15
Qp=1.6x10-19 C Qe = -1.6x10-19 C + - r = 1x10-10 m Example Coulomb’s Law F = k q1q2/r2 k = 9x109 Nm2/C2 F= 2.3x10-8 N 35 Physics 102: Lecture 1, Slide 16
qp=1.6x10-19 C qe = -1.6x10-19 C + - r = 1x10-10 m F ACT: Coulomb’s Law • What is the direction of the force on the proton due to the electron? (A) Left (B) Right (C) Zero • What is the magnitude of the force on the proton due to the electron? Example F= 2.3x10-8 N 38 Physics 102: Lecture 1, Slide 17
ACT A positive and negative charge with equal magnitude are connected by a rigid rod, and placed near a large negative charge. What is the net force on the two connected charges? A) Left B) Zero C) Right Positive charge is attracted (force to left) Negative charge is repelled (force to right) Positive charge is closer so force to left is larger. - + - 43 Physics 102: Lecture 1, Slide 18
ACT: Induced Dipole • An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? 1) Nothing 2) Attracted to charged sphere. 3) Repelled from charged sphere. 45 Physics 102: Lecture 1, Slide 19
ACT: Induced Dipole • An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? 1) Nothing 2) Attracted to charged sphere. 3) Repelled from charged sphere. Physics 102: Lecture 1, Slide 20
ACT: Induced Dipole • An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? 1) Negative charge attracts + repels - Physics 102: Lecture 1, Slide 21
ACT: Induced Dipole • An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? 1) Negative charge attracts + repels - 2) Since + is closer, attractive force is strongest Physics 102: Lecture 1, Slide 22
ACT: Induced Dipole • 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? • 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? 1) Negative charge attracts + repels – 2) Since + is closer, attractive force is strongest Physics 102: Lecture 1, Slide 23
ACT: Induced Dipole • An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released? 1) Nothing 2) Attracted to charged sphere. 3) Repelled from charged sphere. Physics 102: Lecture 1, Slide 24
Summary of Today’s Lecture • The concept of charge • Conductors and insulators • Coulomb’s Law for the force between charges • Much more on Coulomb’s Law in next lecture Physics 102: Lecture 1, Slide 25
Prior to next lecture…. • Read Sections 16.1-6 • Do your prelecture and preflight before 8:00 AM on the day of lecture. See you Wednesday! Physics 102: Lecture 1, Slide 26