PHYS 272 Matter and Interactions II Electric And

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ PHYSICS 272 Electric & Magnetic Interactions You Are in This Section 1 MW 8: 30 -9: 20 AM Prof. Michael Manfra mmanfra@purdue. edu Room: 84, Phone: 43016 Section 2 MW 9: 30 -10: 20 AM Prof. Yong Chen yongchen@purdue. edu The two sections cover the same material Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 1

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Course Content This course deals with electric and magnetic interactions, which are central to the structure of matter, to chemical and biological phenomena, and to the design and operation of most modern technology [foundational to all engineering] The main goal of this course is to have you engage in a process central to science: the attempt to model a broad range of physical phenomena using a small set of powerful fundamental principles. The specific focus of the course is an introduction to field theory, in terms of the classical theory of electricity and magnetism (E&M). The course also emphasizes the atomic structure of matter, especially the role of electrons and protons in matter. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 2

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Schedule • Lectures --- One of the follow sections (Sec. 1): Monday, Wednesday 8: 30 - 9: 20 AM (50 minutes) – Lecture Room: PHYS 112 – Instructor: Prof. Michael Manfra – Office hours: by appointment – Office: PHYS 84 , Phone: (49)-43016 – Email: mmanfra@purdue. edu (please use subject: PHYS 272) (Sec. 2): Monday, Wednesday 8: 30 - 9: 20 AM (50 minutes) – Lecture Room: PHYS 112 – Instructor: Prof. Yong Chen – Office hours: by appointment – Office: PHYS 74 , Phone: (49)-40947 – Email: yongchen@purdue. edu (please use subject: PHYS 272) • Teaching Assistants (Rec/Lab): Jonathan Nistor, David Blasing, Mike Fink, John Doyle, Mark Palenik, Zachary Wolff • Course information: – http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ – Undergraduate Office - PHYS 144 Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 3

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Textbook The textbook is Matter & Interactions, vol II: Electric & Magnetic Interactions by R. Chabay & B. Sherwood (John Wiley & Sons 2011). We will cover almost all of the topics in this volume. See the table of contents at the front of the book (which also includes the contents of Volume I). Make sure it is the Third Edition. The new book comes with a free coupon for Web. Assign, the on-line homework service. Follow the instructions and get yourself registered. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 4

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ General Information Room PHYS 144: Undergraduate office Room PHYS 12: Help center Room PHYS 290: Physics Library We will use Web. Assign for homework and lab assignments. You will be able to access your scores in CHIP. See “Important Links” on course web page for details! For questions concerning Web. Assign contact: V. K. Saxena: Office: PHYS 176, Phone: 49575 Email: saxena@purdue. edu Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 5

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Activities and Responsibilities • In-class activities and responsibilities – You are responsible for attending all classes, and attendance will count toward your grade. – Bring the textbook and a scientific calculator to class. – If you miss class, it is your responsibility to find out what you missed. Lectures slides will be available shortly after lecture concludes. • Recitations and Lab Sessions • Homework – Homework and lab assignments will be posted on the web. See Web. Assign (and Calendar section) for due dates. • Outside class – Study assigned textbook sections. – An assignment to study sections of the textbook means: • Read the assigned textbook sections thoughtfully (try “self-retrieving”). • Do the "stop and think" activities. • Write brief solutions to the in-line "exercises" and keep them in a notebook. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 6

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Quizzes, Exams, Grades • Clicker Questions in Lecture: – Short multiple choice questions will be posed in lecture. The purpose is to assess your understanding. It will also be used to check attendance. We will start counting clicker questions towards your grade at lecture #5. – You have to purchase an i. Clicker ( http: //www. iclicker. com ) from the bookstore. – You must register your clicker ID in CHIP!!!! • Exams: – There will be two 1. 5 -hour exams and a 2 -hour final exam. All exams are closed-book, but relevant formulas and constants will be provided. • Grades: – The final grade will be determined on the following basis (Course Total = 700 points): • 200 points - final exam • 100 points each - two 1. 5 -hour exams (see calendar) • 75 points - Web. Assign homework • 100 points – Labs • 25 points - Clicker Questions & Attendance • 50 points – Weekly Quizzes • 50 points – Recitation Problems Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 7

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ This Week • Study chapter 13 • Lab will start this Wed, Thurs, Friday: Pre. Course Assessment • Do Homework in Web. Assign Announcement Lab Manuals no longer available in Union/Boiler. Copy. Maker Please print your copy BEFORE coming to Lab! Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 8

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Electric and Magnetic Fields Electric and magnetic fields manifest their existence through interactions with matter Maxwell equations: ¶B curl(E) = Ñ ´ E = ¶t Lorentz force: Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 12

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Point Charges • Two types: positive and negative • Like charges: repel • Opposite charges: attract • Charge is quantized in units of e Millikan’s oil drop experiment (1910 -1913) “Fractional” quantized charge (quarks, FQHE…) [not in everyday life] • Point charge: Size is small compared to the distance between it and other objects of interest • Electric charge is an intrinsic property of the fundamental particles that everything is made of • Universe’s Net charge is conserved Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 13

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ The Coulomb Force Law "The magnitude of the electrostatic force between two point charges is directly proportional to the magnitudes of each charge and inversely proportional to the square of the distance between the charges. " Q 1 Q 2 F Charles-Augustin de Coulomb (1736 - 1806) F Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 14

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ The Coulomb Force Law 0 = permittivity constant of vacuum (air is close) r + + 2 F 21 Force on “ 2” by “ 1” 1 Force repulsive + r - F 21 2 1 Force attractive • The force exerted by one point charge on another acts along line joining the charges. • The force is repulsive if the charges have the same sign and attractive if the charges have opposite signs. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 15

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Units and Constants SI units of electric charge: Coulomb, C Constants: 1/4 0 = 9 x 109 N. m 2/C 2 0 = 8. 85 x 10 -12 C 2/N. m 2 permittivity constant of vacuum e = 1. 602 x 10 -19 C (“unit charge’) 1 C = 6. 24 x 1018 elementary charges Particle Charge electron -e positron +e proton +e antiproton -e neutron 0 photon 0 up quark +(2/3)e down quark -(1/3)e Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 16

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Structure of Atom Matter consists of atoms 1 cm 3 : ~1024 atoms Nucleus: ~104 times smaller than electron cloud, ~104 times heavier than electron. 1Å=0. 1 nm=10 -10 m Example: nucleus of the iron atom Size: ~10– 15 m, mass: ~10 -25 kg Nucleus charge = +Ze, atom with Z electrons is neutral. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 17

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ The Concept of Electric Field Accelerates at 9. 8 m/s 2 – why? Accelerates at 1011 m/s 2 – why? There are many possible configurations of charges to produce the observed effect. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 18

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Electric Field There is something in space waiting for a charged particle to interact with it! This virtual force is called electric field. An electric field created by charge is present throughout space at all times, whether or not there is another charge around to feel its effect. Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 19

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Definition of Electric Field Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 20

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Electric Field If our probe charge is positive or negative F due to given E will point in correct direction. Electric field has units of Newtons per Coulomb: [N/C] Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 21

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ The Electric Field of a Point Charge + Including direction: - Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 22

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Example Problem A particle with charge +2 n. C (1 nano. Coulomb=10 -9 C) is located at the origin. What is the electric field due to this particle at a location <-0. 2, -0. 2> m? Solution: 1. Distance and direction: r r = observed _ location - source _ location = -0. 2, -0. 2 - 0, 0, 0 = -0. 2, -0. 2 = r = (-0. 2 )2 + (-0. 2 )2 = 0. 35 m -0. 2, -0. 2 = = -0. 57, -0. 57 0. 35 Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 23

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Example Problem 2. The magnitude of the electric field: 3. The electric field in vector form: Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 24

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ The Physical Concept of ‘Field’ Field: physical quantity, can be scalar or vector Examples: Temperature T(x, y, z, t) --- scale Air flow, gravitational field --- vector m q Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 25

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Forces due to an Electric Field Example: The electric field at a particular location is <-300, 0, 0> N/C. What force would an electron experience if it were placed in this location? Y E e F X Solution: Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 26

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Re-Cap (EMI 14. 1 -14. 3) • Course elements: lecture, recitation, lab, Web. Assign… • Coulomb’s law for electric force • Point charges and unit of charge • Electric force electric field Next time (EMI 14. 4 -14. 8) • Superposition of Electric field due to multiple charges • Electric dipole Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 27

PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http: //www. physics. purdue. edu/academic_programs/courses/phys 272/ Food for Thought: “Coulomb” Blockade Moore’s law Small transistors: Single electron charge matters! To read more: Marc Kastner: “Artificial Atoms”, Physics Today, Jan. 1993, pp 24 “Coulomb blockade lab”: http: //nanohub. org/resources/4231 Fall 2010 Prof. Yong Chen (yongchen@purdue. edu) Prof. Michael Manfra (mmanfra@purdue. edu) Lecture 1 Slide 28