Physics 2102 QuickTime and a TIFF Uncompressed decompressor are needed to see this picture Jonathan Dowling Benjamin Franklin 1705 1790 Physics 2102 Lecture 01 TUE 19 JAN Electric Charge QuickTime and a TIFF Uncompressed decompressor are needed to see this picture QuickTime and a decompressor are needed to see this picture 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 J P Dowling 1994 98 Research Physicist US Army Aviation Missile Command 1998 2004 Principal Scientist NASA Jet Propulsion Laboratory 2004 Present Hearne Institute Office hours Director Nicholson Hall 453 for Theoretical Physics LSU by appointment 12 00N 1 00PM TTh or Email Hearne Institute for Theoretical Physic Quantum Sciences Technologies Group jdowling lsu edu My Own Research Quantum Technologies Photonics Course Details Main Class Website for All Sections http www phys lsu edu classes spring2010 phy s2102 Syllabus Schedule Grading Policy Exam Solutions Lectures will be posted in this section s website http phys lsu edu jdowling PHYS21024SP10 Text Fundamentals of Physics Halliday Resnick and Walker 8th edition We will cover Chapters 21 33 35 36 38 Exams Midterms 6 7PM THU 11 FEB THU 11 MAR THU 15 APR Final Exam 7 30 9 30AM TUE 11 MAY 2010 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 Course Details Grading 100 200 100 50 A 90 1st exam 2nd exam 3rd exam Homework Final Exam 100 B 80 89 C 60 79 59 F 50 D 50 rderline Cases Decided by Class Attendance Checkmar 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 Physical Optics Light Waves Interference QuickTime and a Sorenson Video 3 decompressor are needed to see this picture Let s Get Started Electric Charges wo Types of Charges Positive Negative ike Charges Repel pposite 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 Electric 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 Product of the Magnitudes 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 proportionalit 2 N m k y 8 99 10 9 C2 12 sually we write k 1 4 with 0 8 85 10 0 Units F N Newton q C Coulomb 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 UnitArea is Proportional 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 Example q 1 q2 q3 20 mC 1 d Three Equal Charges Form an Equilateral Triangle d q3 of Side 1 5 m as Shown Compute the Force on q1 d q2 What are the Forces on the Other Charges 60 o F13 1 lution Set up a Coordinate System d mpute Vector Sum of F12 and F13 2 F12 y x d 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 Electric Charges in Solids In Macroscopic Solids Nuclei Often Arrange Themselves Into a Stiff Regular Pattern Called a Crystal Lattice Electrons Move Around This Lattice Depending on How They Move the Solid Can Be Classified by Its Electrical Charges in Solids In a Conductor Electrons Move Around Freely Forming a Sea of Electrons This Is Why Metals Conduct Electricity Charges Can Be Induced Moved Around in Conductors Blue Background Mobile Electrons Red Circles Static Positive Charge Nuclei Insulating Solids In an Insulator Each Electron Cloud Is Tightly Bound to the Protons in a Nucleus Wood Glass Rubber Note That the Electrons Are Not Free to Move Throughout the Lattice but the Electron Cloud Can Distort Locally How to Charge an Object An Object Can Be Given Some Excess Charge Giving Electrons to It We Give It Negative Charge or Taking Electrons Away We Give It Positive Charge How Do We Do Charge an Object Usually Moving Charges From One Surface to Another by Adhesion Helped by Friction or by Contact With Other Charged Objects If a Conductor the Whole Electron Sea Redistributes Itself If an Insulator the Electrons Stay Where They Are Put QuickTime and a TIFF Uncompressed decompresso are needed to see this picture Electroscope http www physicsclassroom com mmedia estatics esn html Van der Graaf Generator http www amasci com emotor vdg ht ttp science howstuffworks com vdg2 htm QuickTime and a Cinepak decompressor are needed to see this picture Conservation of Charge Total Amount of Charge in an Isolated System Is Fixed Conserved Example 2 Identical Metal Spheres Have Charges 1C and 2C You connect these together with a metal wire what is the final charge distribution 1C 2C 1 2 C 1 2 C Quantization of Charge Charge is always found in INTEGER multiples of the charge on an electron proton Unit
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