162. Physics Electricity & Magnetism & Modern Physics Demi-semester III, 2000: Electricity & Magnetism (19 lectures, 3 per week, plus one tutorial per week from week 2) Monday 11am, Thursday 12 noon, Friday 11am, Rivett Lecture Theatre. WWW: http://webraft.its.unimelb.edu.au/640162/pub/index.html Lecturer: Dr Chris. Chantler. Room 505, Physics Building, Tel. [phone]. Text: D.G. Giancoli: Physics, Principles with Applications, 4th edition, 1995 or 5th edition, 1998 (Prentice-Hall). Chapters 16-22. Tennent: Science Data Book (Oliver & Boyd). Prerequisites: Just about none! Except to try to learn and enjoy the information and subject, and to respect the desire of your fellow students to do the same. So try to avoid too much background noise during lectures. This course builds on 161. Broad Objectives: -- comprehend a broad range of elementary physics and develop skills in applying this to important physical and biological systems; -- appreciate the underlying role of physics in science, technology and medicine; -- be able to evaluate experimental data. Assessment: a) Selected problems for developing skills are handed out. They will be referred to in lectures. Some problems are challenging (III or ***) but most reflect the standard of understanding that you are expected to attain by the end of the course. Answers to problems will be distributed at the last lecture of each fortnight. These do not count towards assessment & will be posted on the web. You must have a password like last semester. For details, see http://webraft.its.unimelb.edu.au/. b) Tutorial problems involve selections from problem sheets, recent sections of Giancoli, assignments & other sources. Ask questions in tutorials on issues or problems. Aptitude in tutorials may contribute towards assessment for border-line cases. c) An assignment will be handed out in Week 3. The assignments will not be marked or handed in but should be attempted and discussed in tutorials. This will be equivalent in length to 1/2-hour of an exam & is a good guide to your progress. d) A 30-minute short answer test will be held in the regular tutorial in week 7 (beginning Monday 4th September). This will count 5% towards your final assessment, but will more importantly provide some feedback to you as to your progress and comprehension of the course. Material of the first 6 weeks will be assessed. e) The laboratory assessment and final three-hour examination for Physics 162 are the dominant components of assessment. Approximately half of this exam will be on Electricity and Magnetism. f) On-line modules are available for the Magnetism section, on the Web. These will enhance your understanding of the course material. The modules do not introduce new material and are not examined per se, but material from lectures is enhanced by the modules. Some lunch-time tutorials will be made available to assist you with this. Availability: Your tutor is your first point of reference if you are having trouble with the material covered in the course. If students cannot sort out their problems with their tutors, or if they wish to make suggestions or comments about the way in which the course is delivered, please make an appointment to see me.
How to fail: Your best chance of failing is to (1) have no access to the textbook; (2) miss the lectures, handouts and demonstrations; (3) ignore the problems completely, or maybe look at the solutions in the last week of the course; (4) wait until the tutor forces you to ask or answer a question; and (5) hope that your partner will do most of the work in the labs. How to pass: Physics, in particular, is an integrated subject - each aspect of the course is designed to help you with your understanding of each other aspect. Consequently, if you attend lectures and understand some of what the lecturer is presenting, go away and re-read the textbook carefully, regularly work through problems before the tute and before being given the solutions, and put the effort into the labs, then you will almost certainly pass and will probably enjoy yourself! Course Advice: The first year coordinator, Dr Michelle Livett, is available for course advice. There are a panel of staff members able to assist you, including Dr Chantler. Syllabus: I. Electrostatics: Electric charge; Coulomb's Law; Electric field and lines of force; [Gauss's Law] Electrostatics in biological molecules; Electric dipole moments. [Giancoli, Chapter 16, [Appendix C,4th edn; D,5th edn] and section 17-6] Electric potential and electric energy; Equipotential lines and their relationship with electric field lines; Capacitance; Dielectric materials; Energy density of the electric field; The electrocardiogram. [Giancoli, Chapter 17] Applications of electrostatics: Lightning, Van-de-Graaff generator, Xerography, Electrostatic precipitator, Extra Sensory Perception in Fish. II. Circuit theory: Direct current circuits; Current and Current Density; Electromotive force; Ohm's Law; Resistance and resistivity; Resistance in superconductors; Electric power; Electrical conduction in nerves (qualitative). [Giancoli, Chapter 18] DC Circuit Theory; Kirchhoff's rules; Circuits containing Capacitors and Resistors; Electrical safety. [Giancoli, Chapter 19, excluding 19-10, 19-11] III. Magnetism: Magnetic induction and flux; Magnetic fields of electric currents; Permanent and electro-magnets; Ferromagnetism and magnetic domains; Solenoids; Energy density of the magnetic field; Ampere's Law; Magnetic Forces on Moving Charges and Current-carrying Wires; The Hall effect; Applications including Galvanometers, Electric Motors, Loudspeakers, Mass Spectrometers. [Giancoli, Chapter 20, excluding 20-14]
Electromagnetic Induction; Faraday's Law; Lenz's Law; Electric generators; Transformers; Applications of Induction: microphones and magnetic recording; Eddy Currents. [Giancoli, Chapter 21-1 21-8].
Physics to 162
Understanding Electricity and Magnetism Forces that control the World
Welcome! Your introduction to physics this semester continues from that in first semester. The insights you gained then can and will be used during this course, so you will need to revise concepts of force, motion etc. from time to time. However, the main discussion is about charge, current and magnetism. Most human `high-tech.' technology is based on these concepts, like the Hi-Fi, Fridge, Oven, Air Conditioning, Rockets, Accelerators, Synchrotrons etc., but also things we might take for granted such as Light Bulbs, Static, Batteries, Electricity and even Walking. As a consequence, getting these ideas wrong has profound effects, not just on how we think but also on how we act or react in an emergency or Lightning strike, for example. Equally, getting them right will enable us to comprehend biochemistry, DNA, neurology and many other (complex) issues from a sensible perspective. In other words, this will help with all science courses and many biology courses that you may take in the future; but it will also help in addressing problems in everyday life. The problem is that several of these concepts, including the idea of a potential, the concept of field lines, and the idea of a mathematical integral, are completely new to most of you. This is just like life the most important concepts are often the most difficult. We will avoid unnecessary complexity and give you real and relevant examples but you will still find yourselves challenged more by this course than by first semester. For some this will be frustrating, while others will enjoy and relish the increased challenge. However, your tutors are there to assist you through this, and the course is not at all complete without you consulting with them and sorting these details out in the available tutorials. The course also has direct links with Lab. Work and pracs 13-18.
Schedule: The schedule below is a plan for this section of the course. There will be variations from this plan! References to the text Physics, Principles with Applications (4th or 5th edition) by D C Giancoli may guide your reading in preparation for lectures and during revision between lectures. The questions suggested are selected from earlier editions of Giancoli. You will be provided with solutions to the problem sheets handed out, which are related to these questions and other problems in Giancoli. There are also Concept Tests, which will be given every lecture or so, to check your comprehension of the material presented. Week Lect.Giancoli Concepts: Problem Sheet Questions Demonstrations 1 Mon 16.1- Electric Charge Types & Forces Q1.1,1.2 EL3 Two Balls Repelling, 16.4 EL1 Electroscope Basic structure of atom Balloon Distribution of charge Conductors and insulators Thur 16.5 Polarisation and induced charge Q1.3,1.4 EL1 Electroscope charged by contact or induction 16.6 Electroscope EL2 Electrophorous Coulomb's Law F = k Q1 Q2 /r2 Fri 16.7 Electric Field E=F/q Q1.5-1.9 EL5 field lines 16.8 Point charges and distributions EL6 hollow conductor 2 Mon 16.9 Vector addition of electric fields and forces 16.10 Field lines Electric fields and conductors Measuring charge on electron using electric fields Applications: DNA, Precipitator, Photocopier Thur 17.6 Electric dipole Q2.1-2.4 17.1- Electric potential and potential 17.2 difference V= energy / q Charge movement Electric potential and Electric field V=E/d Fri 17.3- Equipotential lines Q2.5EL4 - capacitor 17.7 2.10 Electron Volt Potential near point charge Parallel plates, Capacitance C = Q/V = 0 A/d
3
Mon
17.817.10 17.11
Thur
Conductors, Dielectrics Storing electrical energy, U = 1/2 Q V Cathode Ray Tube, Thunderstorms Electrocardiograms
3.1-3.3
EL8, EL10 +Pith Balls+Rice Bubbles +hair Slide Show EL12-precipitator Ej1-oscillating potential EKG Lightning, ESP in fish
Fri
18.2 -18.4
4
Mon Thur
Fri
18.518.7 18.8 19.1, 19.2 19.319.7
5
Mon
19.819.11
Circuits, Current I= Q / t and energy delivery Electron-drift in conductors Voltage, Current (DC) and Resistance Ohm's Law V = IR Resistivity , R = L/A Superconductivity Electrical Power P = VI Resistors in Series Rtot = R1 + R2 + & Parallel 1/Rtot = 1/R1 + 1/R 2 + resistor Kirchhoff's Rules: Currents at junctions I1 = I2 + I3 Potential Difference around loop V=0 Sources of PD: emf & internal resistance V = - Ir Dry cells, Rechargeables, Solar Sources in series & parallel Meters AC Circuits V = V0 sin 2 ft, I = I0 sin 2 ft, Vrms = V0 / sqrt(2) Electrical safety: Dry/wet resistance Earthing of appliances
3.4-3.8
3.9-3.21 4.1-4.5
fuse
4.6- 4.9
4.10-4.12 5.0
Thur
Fri
6
Mon
Thur Fri
7
Mon
Thur
20.1-3 Magnets and Magnetism Poles attraction / repulsion Field lines Compasses Atoms as magnets Magnetic fields due to current Right Hand Grip rule Straight wires, Loops, Solenoids Vector addition of Magnetic Fields Forces on currents in magnetic fields 20.4-7 Right Hand (Slap) Rule F = IlB sin Force on charges in magnetic fields F = qvB sin 20.8 More forces on moving charges 20.9 Circular paths, loops, Meters, Motors [20.11 [Hall effect: charge to mass ratio of electrons using electric and magnetic fields] 20.10 Applications of magnetic fields: doorbells, loudspeaker 20.12 21.1- Magnetic Flux vs Electric Flux 21.6 B = BA cos vs B = BA cos Change flux by changing B, A or Faraday's Law = - N B/ t Lenz's Law: Induced current produces magnetic field which opposes flux change Application to combinations of fields and loops Electric Generators Change in flux as coil rotates gives an alternating emf Current induced in loop makes it a magnet that opposes rotation 21.7 Eddy currents, applications to brakes 21.8 Transformers, Voltage ratios equal turns ratios Modern Physics & Optics (17 lectures) new ideas in physics!
5.1-5.3
5.4-5.10
6.1-6.4
6.7,6.8