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Physics 2102 Lecture 01: TUE 19 JANWho am I & Why am I Here?Course DetailsCourse Details: HomeworkCourse Details: GradingWhat Are We Going to Learn? A Roadmap!PowerPoint PresentationLet’s Get Started! Electric Charges…Slide 9Force Between Pairs of Point Charges: Coulomb’s LawCoulomb’s LawSlide 12SuperpositionFeel the Force! ExampleSlide 15Electric Charges in SolidsCharges in SolidsInsulating SolidsHow to Charge an ObjectElectroscopeVan der Graaf GeneratorSlide 22Conservation of ChargeQuantization of ChargeCh. 21: SummarySlide 26QuickTime™ and a decompressorare needed to see this picture.Physics 2102 Physics 2102 Lecture 01: TUE 19 JANLecture 01: TUE 19 JANElectric ChargeElectric ChargePhysics 2102Jonathan DowlingQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Benjamin Franklin (1705–1790)Charles-Augustin de Coulomb (1736–1806)Who am I & Why am I Here?Who am I & Why am I Here?Office hours: Nicholson Hall 453, 12:00N–1:00PM TTh (or by appointment)Email: [email protected] Own Research: Quantum TechnologiesPhotonicsProf. J. P. DowlingHearne Institute for Theoretical Physics Quantum Sciences & Technologies Group1994–98: Research Physicist, US Army Aviation & Missile Command1998–2004: Principal Scientist, NASA Jet Propulsion Laboratory2004–Present: Director, Hearne Institute for Theoretical Physics, LSU 1994–98: Research Physicist, US Army Aviation & Missile Command1998–2004: Principal Scientist, NASA Jet Propulsion Laboratory2004–Present: Director, Hearne Institute for Theoretical Physics, LSUCourse DetailsCourse Details• Main Class Website for All Sections: http://www.phys.lsu.edu/classes/spring2010/phys2102/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.• Lab: Meets This Week! Show up or be dropped!• Tutoring: Free Tutors in 102 Nicholson & 141 Middleton:http://cas.lsu.edu/tutorial-centersCourse Details: Course Details: HomeworkHomeworkWeb-based system: Web Assign To register:• Go to http://www.webassign.net/student.htmlhttp://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.• First HW Is Posted This Week Due Next WED 2AM.Course Details: Course Details: GradingGradingA: ≥90 B: 80-89 C: 60-79 D: 50-59 F: <50100100100502001st exam2nd exam3rd examHomeworkFinal ExamBorderline Cases Decided by Class Attendance Checkmarks!What Are We Going to What Are We Going to Learn?Learn?A Roadmap!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, Diffraction.•Quantum Physics!QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.Let’s Get Started!Let’s Get Started!Electric Charges…Electric Charges…• Two Types of Charges: Positive/Negative• Like Charges Repel• Opposite Charges AttractAtomic StructureAtomic Structure: • Negative Electron Cloud• Nucleus of Positive Protons, Uncharged Neutrons The Unit of Electric Charge isthe “Coulomb” which is “C”.Proton Charge: e = 1.60 × 10–19 CQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Benjamin Franklin (1705–1790)Rules of Electric Rules of Electric Attraction and Attraction and Repulsion Discovered Repulsion Discovered by Benjamin Franklinby Benjamin Franklin12F1q+21F2q−12F1q+21F2q+12F1q−21F2q−Force Between Pairs of Force Between Pairs of Point Charges: Coulomb’s Point Charges: Coulomb’s LawLawCoulomb’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 |F12| = |F21|!!Charles-Augustin De Coulomb (1736–1806)QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.2q−12F1q+21F12rCoulomb’s LawCoulomb’s Law€ F12=k q1 q2r122€ k =14πε0with ε0= 8.85 ×10−12C2N m2€ k = 8.99 ×109N m2C2The “k” is the electric constant of proportionality.Usually, we write:QuickTime™ and a decompressorare needed to see this picture.Units: FM=M[N]M=M[Newton]; rM=M[m]M=M[meter];qM=M[C]M=M[Coulomb]Two Inverse Square LawsTwo Inverse Square LawsQuickTime™ and a decompressorare needed to see this picture.Newton’s Law of Gravitational Force Coulomb’s Law of Electrical Force Area of Sphere = 4r2Number of Lines of Force is Constant. Hence Force Per-Unit-Area is Proportional to 1/r2SuperpositionSuperposition•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!Feel the Force! Feel the Force! ExampleExample•Three Equal Charges Form an Equilateral Triangle of Side 1.5 m as Shown•Compute the Force on q1•What are the Forces on the Other Charges?dq1ddq2q3q1= q2= q3= 20 mCSolution: Set up a Coordinate System, Compute Vector Sum of F12 and F13d123dd12F13Fo60yxQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.What is the Force on Central Particle?Charge +qPlaced at Center Another Example With Another Example With SymmetrySymmetry+qrAll Forces Cancel


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