Physics 102: Lecture 1, Slide 1 Welcome to Physics 102! Electricity + Magnetism Optics Atomic Physics Nuclear Physics Relativity

Physics 102: Lecture 1, Slide 2 Meet the Lecturer George Research –Elementary Particle Experimental Physics

Physics 102: Lecture 1, Slide 3 Course Format (Spiral Learning) Preflights 50 Homework100 Lab 150 Discussion 150 –Take-home quizzes; drop lowest 1 Hour Exams (3 x 100)300 Final Exam

Physics 102: Lecture 1, Slide 4 Grading Scale A A A B B B C C C D D D- <610 F

Physics 102: Lecture 1, Slide 5 Reading & Lecture Do it! Answer preflights 50/1000 points –2 points for honest attempt at preflight. –Must do the entire preflight to earn any credit

Physics 102: Lecture 1, Slide 6 P102 Lectures Not everything you need! –Concepts, Connections, Motivation –Comprehensive Textbook –Calculations Homework + Discussion –Hands-On Lab Taking Notes –Lecture notes will be available at bookstore or online –Some key pieces for you to fill in

Physics 102: Lecture 1, Slide 7 Origin of Charge Charge is an intrinsic property of matter Two types: –Positive Charge: Protons –Negative Charge: electrons –Opposites Attract! (likes repel) Atoms are neutral –Negatively charged electrons “orbit” r~ m –Positively charged central nucleus r~ m

Physics 102: Lecture 1, Slide 8 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? A:

Physics 102: Lecture 1, Slide 9 Electroscope 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 10 ACTS A negatively charged rod is used to charge an electroscope by induction. What is the resulting net charge on the electroscope? 1) positive2) zero3) 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. 1) positive2) zero3) negative

Physics 102: Lecture 1, Slide 11 ACTS A negatively charged rod is used to charge an electroscope by induction. What is the resulting net charge on the electroscope? 1) positive2) zero3) 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. 1) positive2) zero3) 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 Force on electron in Hydrogen atom

Physics 102: Lecture 1, Slide 13 ACT: Coulomb’s Law What is the direction of the force on the proton due to the electron? (1) Left(2) Right(3) 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= _______ N F

Physics 102: Lecture 1, Slide 14 ACT: Coulomb’s Law What is the direction of the force on the proton due to the electron? (1) Left(2) Right(3) 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 15 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? 1) Left2) Zero3) Right

Physics 102: Lecture 1, Slide 16 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? 1) Left2) Zero3) Right

Physics 102: Lecture 1, Slide 17 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 18 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 19 ACT: Induced Dipole 1) Negative charge attracts + repels - An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released?

Physics 102: Lecture 1, Slide 20 ACT: Induced Dipole 2) Since + is closer, attractive force is strongest 1) Negative charge attracts + repels - An uncharged conducting sphere is hung next to a charged sphere. What happens when the uncharged sphere is released?

Physics 102: Lecture 1, Slide 21 ACT: Induced Dipole 1)Negative charge attracts + repels – 2) Since + is closer, attractive force is strongest 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?

Physics 102: Lecture 1, Slide 22 To Do Read Sections Do your preflight before 8:00 AM on the day of lecture. See you next time!