Lecture1 - Lecture 1 - Coulomb’s Law Lecture Chapter 25 -...

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Unformatted text preview: Lecture 1 - Coulomb’s Law Lecture Chapter 25 - Tuesday January 9th •Introduction and overview of the course •Discussion of syllabus and policies •Overview of the course web page •Electrostatics •Charge and charging •Conductors and insulators •Coulomb’s Law •Scalar and vector notation •Discrete charge distributions (superposition principle) •Continuous charge distributions Reading: pages 567 thru 580 (chapter 25) in HRK Read and understand the sample problems WebAssign assignment: set 1, due Thu. 18th at 11:59pm There is also a practice assignment (not counted in grade) Graded problem: Ch. 25 – Prob. 10 Practice problems: Ch. 25 - Ex. 1, 9, 19; Prob. 3 & 11 The PHY2061 Course Web Site http://www.phys.ufl.edu/~hill/teaching/2005/2061/index.htm •All information is posted here •Syllabus, homework and exam policies, etc.. •Links to on-line homework pages (incl. deadlines) •Course schedule with exam dates •Solutions to exams (and practice questions) •DON’T FORGET TO DO THE DAILY HOMEWORK!! •No excuse for not getting close to 100% for the weekly (WebAssign) homework sets •YOU NEED TO PURCHASE REMOTES FOR THE IN-CLASS QUIZZES (CONSULT THE COURSE WEB PAGE) About the text book About •Many useful exercises and problems at ends of chapters •Multiple choice questions (may be used for JiTT/HiTT) •Conceptual questions (ask me if you do not understand) •Exercises are similar to the example problems in main text •Problems require thinking outside of the box •All odd numbered Exercises and Problems have the numerical answers at the back of the text book •I will assign a few of these problems as optional work, and I will post solutions after the corresponding WebAssign deadlines •Take some time to study the appendices at the end of the book. In particular, you will find integrals and other useful trigonometric identities. The PHY2061 grading The PHY 2061 (spring 2005/2006) 8 Mean = 75% Median = 80% 50% of class scored above 80% 70% of class scored above 70% Number of students 6 B+ 2 years of 2061: A 20 A (36%) 14 B+ (25%) 11 B (20%) 7 C (13%) 2 D (4%) Note 82% A/B+/B B C 4 2 F D 0 20 30 40 50 60 70 80 90 100 Score (%) •DON’T FORGET TO DO THE DAILY HOMEWORK!! •YOU NEED TO PURCHASE REMOTES FOR THE INCLASS QUIZZES (1ST TRIAL ON THURSDAY). •ON-LINE HOMEWORK. DO THE HOMEWORK & COME TO CLASS DO 100 PHY 3513 (Fall 2005) • Clear correlation between homework and exam scores. • Nevertheless, the exams require understanding, i.e. you will not get away with memorization of homework problems. Overall Grade 90 80 70 60 50 40 20 30 40 50 60 70 80 90 100 110 Score on Homework •IF YOU ARE HERE ONLY FOR THE GRADE, THE CHANCES ARE HIGH THAT YOU WILL DO POORLY. •THIS IS AN ENRICHED COURSE – YOU ARE HERE TO LEARN. PHY2060 - What causes acceleration? PHY2060 Linguistic arguments: • Some sort of interaction - loosely speaking, a push or a pull on an object. • We call this a force, which can be said to act on a body. force • Examples of forces: Normal or "contact force" Gravitational force Electromagnetic force Weak and strong nuclear forces We'd better be more We'd scientific about this... The main subject of this course The Electrostatics Source charges do t’s Le me so ts en ri m pe ex Test charge Charges of the same sign repel one another, charges of opposite sign attract one another. What is charge? What •Charge is measured in Coulomb’s (C) • Fundamental unit. • Definition based on forces between current carrying wires (current = Ampères, or C/s), i.e. chapter 33. •Charge is discrete • Thompson discovered the electron in 1896. He found that charge was carried by elementary particles with the same charge to mass ratio. • The elementary charge of the electron was not measured until 1909 (Millikan). • Both experiments earned Nobel prizes. Charge on an electron: 1 Coulomb of charge: 1 Ampère (= 1 C/s) Charge is discrete: e = 1.6 × 10−19 Coulombs 6.24 × 1018 electrons 6.24 × 1018 electrons/second q = ne n = ±1, ±2, ±3,... Static electricity through charging Static Conductor Insulator Electrical discharge Electrical Methods of charging Methods Coulomb’s Law Coulomb Coulomb’s torsional balance Coulomb 1785 q1 q2 F∝ , 2 r K= 1 4πε o or q1 q2 F=K r2 = 8.99 × 109 N ⋅ m 2 / C2 εο = 8.85418781762 × 10-12 C2/N·m2 1 εo = 4π × 10−7 N ⋅ s2 / C2 ) × c 2 ( c = speed of light in vacuum = 299792458 m/s “Electrodynamics in a nutshell” 1 qQ ˆ F= r 2 4πε o r ˆ r Mix in a little relativity q Q ∫ E ⋅ dA = q εo dΦB ∫ E ⋅ d s = − dt ∫ B ⋅ dA = 0 dΦE ∫ B ⋅ d s = μoi + μoε o dt Coulomb’s Law in vector notation Coulomb 1 q1q2 ˆ F12 = r12 = − F21 2 4πε o r12 1 q1q2 ˆ F21 = r21 2 4πε o r21 r12 ˆ ˆ r12 = = −r21 r12 Superposition principle Superposition Source charges Test charge q0 Fq0 = F1 + F2 + F3 + ...Fi = ∑ Fi i •Leads to Maxwell’s equations being linear. Calculus (continuous charge distribution): ˆ F = ∫ dF = iˆ ∫ dFx + ˆ ∫ dFy + k ∫ dFz j 1 q0dq dF = 2 4πε o r q0 = test charge ...
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This note was uploaded on 07/28/2011 for the course PHY 2061 taught by Professor Fry during the Spring '08 term at University of Florida.

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