Welcome to Physics 202

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1 Welcome to Physics 202 Todays Topics The Physics 202 Team Course Formality and Course Overview Q&A Ch 21: Electric Charges Physics 202 Homepage (under construction, almost done) Physics Department Homepage

2 The Physics 202 Team Faculty (lectures): Prof. Matthew Herndon, 4279 Ch Prof. Gary Shiu, 5279 CH Teaching Assistants (labs, discussions): Daniel Crow Scott Douglass Yutao Gong Taylor Klaus Aaron Levine Andrew Loveridge Jason Milhone Hojin Yoo

3 Physics 202 Course Composition Text: EText: Tipler and Mosca, Physics for Scientists and Engineers, 6th ed Lectures: TR 1:20 pm (Lec. 1), 2:25 pm (Lec. 2) (you can attend either) Discussion Sessions: 2/week. (Grading: quizzes, attendance) Labs: Mandatory. Each missing lab = - 1 letter grade level (AàAB,ABàB...) Homework: ~10 problems/week online by Webassign.net Exams: (3 middle-terms + final) Office Hours. (Faculty: by appointments, TAs: as scheduled) Your home time: > 4 hours/week + homework. Honor credit: announcement latter this week Grading: Homework: 200 pts Laboratory: 100 pts (plus missing lab penalty) Discussion: 100 pts Midterm 1: 100 pts Midterm 2: 100 pts Midterm 3: 100 pts Final Exam: 200 pts (Final grades are based on curved component scores)

4 Lectures Style: PPT + white board + demos Subjects: Key concepts. Interactive problem solving Lectures are NOT meant to be complete. In addition to your own study of the subject Do read materials BEFORE the lecture. Our lectures are designed with the assumption that you ve read the corresponding sections! Review materials after the lectures. Lecture notes will be posted after each lecture Physics is about solving problems. In this case problems relevant to engineers and scientists. There is no substitute for experience solving problems. Learning Physics: Preview + Lecture + Review + Application to Problems

5 Exam Dates: Exams and Exam Policy Midterms (5:30-7:00 pm, rooms TBA) Exam 1: Wednesday Oct 5 th Exam 2: Wednesday Nov 2 nd Exam 3: Wednesday Nov 30 th Final: Tuesday Dec 20 (7:25-9:25 pm, rooms TBA), cumulative. If you have a conflict with above exam dates, inform your professors asap, at least 2 weeks before the scheduled date. Alternative exam arrangements are granted only for valid reasons. Valid excuses: University Academic/athletic conflicts Medical emergency Legal obligations

6 Course Web: Some Practical Issues (under construction nearly done) When sending us s: Include word 202 somewhere in the subject line. (phy202, physics 202, p202, or simply 202 will do) Mentioning your section # is essential. Homework assignments are posted each Tuesday before lecture and due by 11 pm of the following Monday. Lecture notes will be posted after each lecture on the same day. Follow the links on course web. One discussion session, no labs this (first) Week Please all sign up for WebAssign. ( 6

7 Light and Optics Electro-Magnetism Thermodynamics Heat, Temperature, Pressure, Entropy,.. Oscillation and Waves Classical Mechanics Laws of motion Force, Energy, Momentum, Physics 201 and 202 Cosmology Sub-Sub-Atomic: Elementary Particles Sub-Atomic: Nuclear Physics Many-Atoms: Molecules, solids Atomic Structure Quantum Theory Relativity Classical Modern

8 Before Physics 202 Mechanics Gravitation Waves Thermodynamics Mechanics: Motion and Force Fundamental Laws: Newtons laws of motion (Classical view) Energy/Momentum/Angular Momentum conservation (modern view) Gravitation: One of the four fundamental forces Fundamental Law: Newtons Law of Universal Gravitation. Waves: Coherent phenomena over space and time Fundamental Law: Superposition Principle Thermodynamics: Statistical behavior of large quantity Fundamental Laws: Laws of Probability (average, entropy, ) + Laws of Physics.

9 Physics 202 Electro-Magnetism Light &Optics Electro-Magnetism: Electric force, electric charge, electric fields àch. 21,22 Electric potential à Ch. 23 Current, capacitance & resistance à Ch. 24, 25 Magnetic fields and magnetic force à Ch. 26, 27, 28 DC and AC Circuits à Ch. 29 Electromagnetic waves à Ch. 15, 30 Light and Optics Physics of light Electromagnetic waves à Ch. 30 Properties of light à Ch. 31 Lights as rays: Geometric optics, imaging à Ch. 32 Lights as (electromagnetic) waves, interference àch. 33

10 Demo: Two Types of Electric Charges Opposite signs attract Like signs repel

11 Properties of Electric Charges 2+1 types: positive, negative (+neutral). Unit: Coulomb (C). 1 C= charge of 6.24x electrons, +protons. Electric charge is quantized: q=±ne, e=1.602x10-19 C Building blocks of matters: Charge (C) Mass (kg) Electron -e - =-1.602x x10-31 Proton e=+1.602x x10-27 Neutron x10-27 Electric charge is conserved: charges can be moved around, but the total charge remains the same. For very deep thinkers: Why electrons and protons have the same electric charge?

12 What Are Happening in Previous Demo Initially both the rod and the fur are neutral Neutral ßà the object carries equal amount of negative (electron) and positive (protons) charges. When the rod is rubbed against the fur, electrons are separated from the protons and transferred from one objects to another. The result is that the rod (and the fur) now have un-equal mount of charges à they are charged (charge by friction) rubber rods tend to acquire more electron à negative glass/acrylic rods tends to lose electron à positive Attraction/repel behavior can be explained by the rules: Like sign charges repel each other Opposite sign charges attract each other.

13 One More Demo: Electroscope, Charge by Induction Remember: Like signs attract, opposite signs repel Conductivity of matter: Conductors (metals): electrons are free to move (protons do not move) Insulators (glass, plastic, most fabric): charges can not move (or at least fairly difficult to move them) Semi-conductors : charges have limited mobility, future topics 13

14 A Repeated Message Lectures supplement but do not substitute for reading and solving problems! Learning Physics: Preview + Lecture + Review + Application to Problems

15 Review: Before Thursday (Read Ch. 23) Electric charge is an intrinsic property of matter. There are two types of charges: positive and negative. Preview: A particle (an object) can have three charge states: positive, negative, neutral Electric forces exist between two charged particles Like sign changes repel one another Opposite sign charges attract one another. Electric forces are quantified by Coulombs Law A charged particle creates an electric field around it. Electric field exerts electric forces on charged particles. General ideas on how to calculate electric field.

16 Electric Force And Coulombs Law Electric forces exist between two charged particles The direction of electric force depends on the signs of the charges: forces between opposite sign charges are attractive forces between like sign charges are repulsive The magnitude of the electric forces for point charges F 12 = F 21 = k e q 1 r q 2 2 (Coulombs Law) Coulomb Constant: k e = 8.987x10 9 Nm 2 /C 2 = 1/(4πε 0 ) ε 0 : permitivity of free space (Ch. 26)

Welcome to Physics 202

Welcome to Physics 202 Todays Topics The Physics 202 Team Course Formality and Course Overview Q&A Ch 23: Electric Charges Physics 202 Homepage http://www.physics.wisc.edu/undergrads/courses/fall2012/202/index.html