Physics 2102 QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Jonathan Dowling Benjamin Franklin 1705 1790 Physics 2102 Lecture 01 MON 12 JAN Electric Charge I QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Version 01 14 19 Charles Augustin de Coulomb 1736 1806 QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Who am I Why am I Here Prof Jonathan P Dowling 1994 98 Research Physicist US Army Aviation Missile Command 1998 2004 Principal Scientist NASA Jet Propulsion Laboratory 2004 Present Director Hearne Institute Theoretical Office hours Nicholson Hall 453 MWF for 10 30 Physics LSU 11 30AM or by appointment Phone 225 578 0887 Hearne Institute for Theoretical Physics Quantum Sciences Technologies Grou Email jdowling lsu edu My Own Research Quantum Optics Quantum Computing Photonic Crystals Course Details Main Class Website for All Sections http www phys lsu edu classes spring2009 phy s2102 Syllabus Schedule Grading Policy Exam Solutions Lectures will be posted in this section s website http phys lsu edu jdowling PHYS21022SP09 Text Fundamentals of Physics Halliday Resnick and Walker 8th edition We will cover chapters 21 36 Exams Midterms 6 7PM THU 05 FEB THU 05 MAR THU 02 APR Final Exam 5 30 7 30PM FRI 08 MAY Lab Meets This Week Show up or be dropped Course Details Homework Web based system Web Assign To register Go to http www webassign net student html On the left frame student login Username pawsusername lsu Institution lsu Password lsuidnumber Choose credit card registration or FREE with Purchase of PHYS2102 Book from Bookstore One Assignment Per Week Due 2AM Wednesdays Course Details Grading 100 200 100 30 A 90 1st exam 2nd exam 3rd exam Homework Final Exam 100 B 80 89 C 60 79 50 D 50 59 Borderline Cases Decided by Class Attendance F What Are We Going to Learn A Roadmap Electric Charge Electric Force on Other Electric Charges Electric Field and Electric Potential Moving Electric Charges Current Electronic Circuit Components Batteries Resistors Capacitors Electric Currents Magnetic Field Magnetic Force on Moving Charges Time Varying Magnetic Field Electric Field More Circuit Components Inductors AC Circuits Maxwell s Equations Electromagnetic Waves Light Waves Geometrical Optics Light Rays Let s Get Started Electric Charges Two Types of Charges Positive Negative ike Charges Repel Opposite Charges Attract Atomic Structure Structure Negative Electron Cloud Nucleus of Positive Protons Uncharged Neutrons The Unit of Electric Charge is the Coulomb which is C QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Benjamin Franklin 1705 1790 Rules of Attraction and Repulsion Discovered by Benjamin Franklin QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Force Between Pairs of Point Charges Coulomb s Law QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Charles Augustin De Coulomb 1736 1806 q1 F12 q 2 F21 F12 q1 q 2 F21 F12 q1 q 2 F21 Coulomb s Law the Force Between Point Charges Lies Along the Line Connecting the Charges Is Proportional to the Magnitude of Each Charge Is Inversely Proportional to the Distance Squared Note That Newton s Third Law Says F 12 F21 Coulomb s Law QuickTime and a decompressor are needed to see this picture q1 F12 F21 r12 k q1 q2 F12 2 r12 q 2 The k is the electric constant of proportionality 2 N m k 8 99 10 9 C2 12 Usually we write k 1 4 with 0 8 85 10 0 Units F N Newton r m meter C2 N m2 Two Inverse Square Laws Newton s Law of Gravitational Force Coulomb s Law of Electrical Force Area of Sphere 4 r2 QuickTime and a decompressor are needed to see this picture Number of Lines of Force is Constant Hence Force Per Unit Area is Proportional to 1 r2 Superposition Question How Do We Figure Out the Force on a Point Charge Due to Many Other Point Charges Answer Consider One Pair at a Time Calculate the Force a Vector In Each Case Using Coulomb s Law and Finally Add All the Vectors Superposition Useful To Look Out for SYMMETRY to Simplify Calculations QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Feel the Force q q q 20 mC Example q 1 2 3 1 d Three Equal Charges Form an Equilateral Triangle of d q3 Side 1 5 m as Shown Compute the Force on q1 d q2 What are the Forces on the Other Charges Solution Set up a Coordinate System Compute Vector Sum of F12 and F13 60 o F13 1 F12 y d d 2 x 3 d Another Example With Symmetry r k 2q q F r2 r q Charge q Placed at Center F What is the Force on Central Particle All Forces Cancel Except From 2q QuickTime and a TIFF Uncompressed decompressor are needed to see this picture
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