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Physics54S09I

Physics54S09I - PHY 54 Course Structure L1 Focus Wave...

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Unformatted text preview: PHY 54 Course Structure L1 Focus: Wave properties of light—electromagnetic fields Lecture: 1) Brief power point review of material in reading assignment. BlackBoard Site — bring printout of lecture PDF to class. 2) Example HW problems—get started! 3) DEMOS 4) PRS problems Attendance is NOT graded! Lecturer: John E. Thomas—optical trapping of ultracold atoms. Office: Physics 185, E-mail: jet @ phy.duke.edu, Phone: 660-2508. Office hours: By e-mail appointment. PHY 54 Course Structure L1 Homework: 1) New HW and material in Lecture every Thursday due the following Thursday. See BlackBoard site. 2) HW is NOT graded. Feel free to work together and discuss HW problems, use Help Room, etc. 3) Homework Quiz in recitation. Recitation: 1) Brief review of lectures from the prior week . 2) Go over HW — small groups and whole class. 3) Quiz at the end of recitation—focus one HW problem. 4) Instructor determines your grade and writes letters of recommendation. Labs: 1) Experiments linked to lecture concepts. 2) Lab write ups. PHY 54 Course Structure L1 Grading: 1) Two Exams 20% each (40% total). 2) Final Exam 30% 3) Homework Quizzes 15% (drop lowest) 4) Labs 15% (drop lowest) Ch 21: Electric Charge and Electric Field L1 Focus: Charges and Vector addition of forces on charges: Find Net Force on charge 2 +q 2 +Q 1-Q 3 F 3 on 2 F net F 2 on 1 ? x y If arrows are in correct proportion, which charge has a larger magnitude, 1 or 3? What is the magnitude of each force? Direction of F 1 on 2 ? F 1 on 2 Along line between centers of charges Key idea: Force vectors add independently (linear superposition principle) Ch 21: Electric Charge and Electric Field L1 Memorize this! Magnitude of the Force: Coulomb’s Law (1736-1806) 2 2 1 r Q Q k F = Magnitude of the Force Product of magnitudes of charges/distance squared 2 2 9 / 10 . 9 C m N k ⋅ × = Two 1 C charges at 1 m: N F 9 10 . 9 × = 2.2 lbs = 9.8 N 1 million tons! Approach: 1) Find the magnitude of each force on a given charge using the magnitudes of the charges 2) Find the direction of each force 3) Add vector components along x, y to find resultant Ch 21: Electric Charge and Electric Field L2 Focus: Electric fields: Why define a field ?-Q 3 +q 2 +Q 1 F 1 on 2 F 3 on 2 F net x y Key idea: What happens to the net force on 2 if q 2 doubles, triples, quadruples, halves? Direction? Magnitude? * For fixed positions and charges of 1 and 3, find E and then know F net for any q 2 . F net is along the direction of E DO YOU BELIEVE in FIELDS ?!! Put your hand in a laser beam! Memorize this! F net = q 2 E Define field E (for q 2 > 0) CO 2 Laser Beam Stable Commercial Laser 140 Watt CO 2 Laser Invisible infrared beam λ = 10.6 μ m Ch 21: Electric Charge and Electric Field L2 Electric field of a point charge Q 1 : +Q 1 2 1 r Q k E = Magnitude of Field: F = q 2 E 2 F = q 2 E 2 2 2 1 2 r q Q k F E q = = Magnitude of Force: F = q 2 E Direction of Field: Radially outward F = F 1 + F 2 + F 3 + …. = q 2 ( E 1 + E 2 + E...
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Physics54S09I - PHY 54 Course Structure L1 Focus Wave...

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