Physics 102: Lecture 1, Slide 1 Welcome to Physics 102! Electricity + Magnetism (at the heart of most processes around us: …in atoms & molecules; living cells) Optics Atomic Physics Nuclear Physics Relativity Please turn cell phones off

Physics 102: Lecture 1, Slide 2 Meet the Lecturer Research: ___________________________________ Office Hours: ______________

Physics 102: Lecture 1, Slide 3 Course Format Daily Planner –what you should be doing and when you should be doing it Course Description Required Materials –Be sure to register your I-Clicker prior to lecture Lectures –posted just after the lecture is given First Discussion: __________ First Lab: ____________ Exam dates:________________________

Physics 102: Lecture 1, Slide 4

Physics 102: Lecture 1, Slide 5 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 6 Grading Preflights & Lectures 50 Homework100 Lab (Prelab due at start of lab)150 Discussion 150 –Take-home quizzes; drop lowest 1 Hour Exams (3 x 100)300 Final Exam

Physics 102: Lecture 1, Slide 7 Grading Scale A A A B B B C C C D D D- <610 F

Physics 102: Lecture 1, Slide 8

Physics 102: Lecture 1, Slide 9 Prelectures & ACTS Do it! Answer preflights 50/1000 points –1 point for honest attempt at preflight. –1 point for using clicker in lecture (ACTS) 2 points/lecture x 25 lectures = 50 points Note that there are 28 lectures, so you have some free ones Register I-Clicker before lecture

Physics 102: Lecture 1, Slide 10 Physics 101 Electricity+Magnetism Circuits Optics Modern Atomic Nuclear Relativity Physics 102 Content Kinematics Forces Energy Fluids Waves (Sound) MacroscopicMicroscopic

Physics 102: Lecture 1, Slide 11 Origin of Charge Charge is an intrinsic property of matter Two types: –Positive Charge: e.g. protons –Negative Charge: e.g. electrons –Opposite charges attract. Like charges repel. –The electric force is what holds stuff together Atoms are neutral –Negatively charged electrons “orbit” around positively charged central nucleus

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Physics 102: Lecture 1, Slide 13 Conductors and Insulators 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?

Physics 102: Lecture 1, Slide 14 Electroscope (+demo) Conduction –Charged rod is brought near scope –Charged rod touches scope transferring some charge –Scope is left w/ same charge as rod 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

Physics 102: Lecture 1, Slide 15 Draw: Electroscope conduction & induction

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Physics 102: Lecture 1, Slide 17 ACTS A negatively charged rod is used to charge an electroscope by induction. What is the resulting net charge on the electroscope? A) positiveB) zeroC) 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) positiveB) zeroC) negative

Physics 102: Lecture 1, Slide r = 1x m Q p =1.6x C Q e = -1.6x C Coulomb’s Law Magnitude of the force between charges q 1 and q 2 separated a distance r: F = k q 1 q 2 /r 2 k = 9x10 9 Nm 2 /C 2 Magnitude and direction Solve! Force on electron in Hydrogen atom

Physics 102: Lecture 1, Slide 19 Coulomb’s Law F = k q 1 q 2 /r 2 k = 9x10 9 Nm 2 /C r = 1x m Q p =1.6x C Q e = -1.6x C Solution: F= 2.3x10 -8 N Magnitude and direction

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Physics 102: Lecture 1, Slide 21 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? + - r = 1x m q p =1.6x C q e = -1.6x C F= 2.3x10 -8 N F

Physics 102: Lecture 1, Slide 22 ACT +- - Positive charge is attracted (force to left) Negative charge is repelled (force to right) Positive charge is closer so force to left is larger. 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) LeftB) ZeroC) Right

Physics 102: Lecture 1, Slide 23 ACT: Induced Dipole 1) Nothing 2) Attracted to charged sphere. 3) Repelled from charged sphere. An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released?

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Physics 102: Lecture 1, Slide 25 Draw what happens:

Physics 102: Lecture 1, Slide 26 ACT: Induced Dipole 1) Nothing 2) Attracted to charged sphere. 3) Repelled from charged sphere. An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released?

Physics 102: Lecture 1, Slide 27 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 28 Prior to next lecture…. Do your prelecture and preflight before 6:00 AM on the day of lecture.